refactor: update imports to use ES module syntax and improve test structure (#1350)

- Changed import statements across multiple files to use the .js extension for ES module compatibility.
- Refactored test files to utilize jest's unstable_mockModule for mocking core actions.
- Removed unnecessary spy instances in tests, replacing them with direct mocked function calls.
- Updated TypeScript configuration to target ES2022 and use NodeNext module resolution.
- Removed the tsconfig.spec.json file and adjusted the main tsconfig.json to exclude test files.

.licenses/npm/@actions/io.dep.yml

@@ -1,6 +1,6 @@
 ---
 name: "@actions/io"
-version: 2.0.0
+version: 3.0.2
 type: npm
 summary: Actions io lib
 homepage: https://github.com/actions/toolkit/tree/main/packages/io