Migrate to ESM and upgrade dependencies

[priyagupta108]

Description:
Convert to ESM, update imports/tests/configs for ESM, and bump dependencies.

Related issue:
Add link to the related issue.

Check list:

• Mark if documentation changes are required.
• Mark if tests were added or updated to cover the changes.

[Copilot]

Pull request overview

This PR migrates the action’s TypeScript codebase to ESM (NodeNext) and updates the toolchain/configuration to support ESM linting and testing, alongside a broad dependency refresh.

Changes:

• Switch TypeScript compilation to NodeNext and update internal imports / __dirname usage for ESM.
• Replace legacy ESLint/Jest/Prettier configs with ESM-friendly equivalents and update tests to ESM mocking patterns.
• Bump runtime/dev dependencies and refresh licensed metadata to match new dependency graph.

Reviewed changes

Copilot reviewed 67 out of 78 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
tsconfig.json	Switch TS module system to NodeNext
tsconfig.eslint.json	Add dedicated TS config for ESLint
src/setup-dotnet.ts	Update imports and ESM path resolution
src/installer.ts	Update imports and ESM path resolution
src/cache-utils.ts	Update relative import to .js specifier
src/cache-save.ts	Update relative imports to .js specifiers
src/cache-restore.ts	Update relative imports to .js specifiers
package.json	Mark package as ESM; bump deps/scripts
jest.config.ts	New TS-based Jest config for ESM + ts-jest
jest.config.js	Remove legacy CommonJS Jest config
eslint.config.mjs	New flat ESLint config for ESM/TS
dist/setup/package.json	Mark bundled setup output as ESM
dist/cache-save/package.json	Mark bundled post step output as ESM
.prettierrc.json	Add JSON-based Prettier config
.prettierrc.js	Remove legacy CommonJS Prettier config
.licenses/npm/yallist.dep.yml	Remove outdated licensed entry
.licenses/npm/wrappy.dep.yml	Remove outdated licensed entry
.licenses/npm/universal-user-agent.dep.yml	Update licensed metadata for new version
.licenses/npm/semver.dep.yml	Update licensed metadata for new version
.licenses/npm/semver-7.6.0.dep.yml	Remove outdated licensed entry
.licenses/npm/once.dep.yml	Remove outdated licensed entry
.licenses/npm/ms.dep.yml	Update licensed metadata for new version
.licenses/npm/minimatch-3.1.5.dep.yml	Add licensed metadata for dependency
.licenses/npm/minimatch-10.2.5.dep.yml	Add licensed metadata for dependency
.licenses/npm/lru-cache.dep.yml	Remove outdated licensed entry
.licenses/npm/json-with-bigint.dep.yml	Update licensed metadata for dependency change
.licenses/npm/fast-xml-parser.dep.yml	Update licensed metadata for new version
.licenses/npm/deprecation.dep.yml	Remove outdated licensed entry
.licenses/npm/debug.dep.yml	Update licensed metadata for new version
.licenses/npm/content-type.dep.yml	Add licensed metadata for dependency
.licenses/npm/brace-expansion-5.0.6.dep.yml	Add licensed metadata for dependency
.licenses/npm/brace-expansion-1.1.15.dep.yml	Add licensed metadata for dependency
.licenses/npm/before-after-hook.dep.yml	Update licensed metadata for new version
.licenses/npm/balanced-match-4.0.4.dep.yml	Add licensed metadata for dependency
.licenses/npm/balanced-match-1.0.2.dep.yml	Add licensed metadata for dependency
.licenses/npm/@typespec/ts-http-runtime.dep.yml	Update licensed metadata for new version
.licenses/npm/@octokit/types.dep.yml	Update licensed metadata for new version
.licenses/npm/@octokit/types-13.10.0.dep.yml	Remove outdated licensed entry
.licenses/npm/@octokit/request.dep.yml	Update licensed metadata for new version
.licenses/npm/@octokit/request-error.dep.yml	Update licensed metadata for new version
.licenses/npm/@octokit/plugin-rest-endpoint-methods.dep.yml	Update licensed metadata for new version
.licenses/npm/@octokit/plugin-paginate-rest.dep.yml	Update licensed metadata for new version
.licenses/npm/@octokit/openapi-types.dep.yml	Update licensed metadata for new version
.licenses/npm/@octokit/graphql.dep.yml	Update licensed metadata for new version
.licenses/npm/@octokit/endpoint.dep.yml	Update licensed metadata for new version
.licenses/npm/@octokit/core.dep.yml	Update licensed metadata for new version
.licenses/npm/@octokit/auth-token.dep.yml	Update licensed metadata for new version
.licenses/npm/@azure/storage-common.dep.yml	Update licensed metadata for new version
.licenses/npm/@azure/storage-blob.dep.yml	Update licensed metadata for new version
.licenses/npm/@azure/core-xml.dep.yml	Update licensed metadata for new version
.licenses/npm/@azure/core-rest-pipeline.dep.yml	Update licensed metadata for new version
.licenses/npm/@azure/core-http-compat.dep.yml	Update licensed metadata for new version
.licenses/npm/@azure/core-client.dep.yml	Update licensed metadata for new version
.licenses/npm/@azure/abort-controller.dep.yml	Add licensed metadata for dependency
.licenses/npm/@actions/io.dep.yml	Update licensed metadata for new version
.licenses/npm/@actions/http-client-4.0.1.dep.yml	Update licensed metadata for new version
.licenses/npm/@actions/glob-0.7.0.dep.yml	Correct/update licensed metadata entry
.licenses/npm/@actions/glob-0.6.1.dep.yml	Update licensed metadata for new version
.licenses/npm/@actions/github.dep.yml	Update licensed metadata for new version
.licenses/npm/@actions/exec.dep.yml	Update licensed metadata for new version
.licenses/npm/@actions/core.dep.yml	Update licensed metadata for new version
.licenses/npm/@actions/cache.dep.yml	Update licensed metadata for new version
.licensed.yml	Allow/review new licenses introduced by bumps
.eslintrc.js	Remove legacy ESLint config
.eslintignore	Remove legacy ESLint ignore file
tests/setup-dotnet.test.ts	Convert tests to ESM module mocking/imports
tests/latest-version.test.ts	Convert tests to ESM module mocking/imports
tests/installer.test.ts	Convert tests to ESM module mocking/imports
tests/installation-scripts.test.ts	Fix __dirname usage for ESM tests
tests/csc.test.ts	Update JSON import + TS indexing workaround
tests/cache-utils.test.ts	Convert tests to ESM module mocking/imports
tests/cache-save.test.ts	Convert tests to ESM module mocking/imports
tests/cache-restore.test.ts	Convert tests to ESM module mocking/imports
tests/authutil.test.ts	Fix __dirname usage + ESM import specifiers
tests/snapshots/authutil.test.ts.snap	Update snapshot header text

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[Frulfump]

This should fix #731
So maybe worth to link with a "Fixes ..." comment?

[Frulfump]

https://github.com/actions/setup-dotnet/actions/runs/28232146400/job/83638225574#step:9:1

Reports 18 moderate severity vulns so would be good to fix those as well.