Migrate from mocha to Node.js native test runner

Includes coverage reports when using Node.js 22 onwards

.github/CONTRIBUTING.md

@@ -6,8 +6,6 @@ Hello, thank you for your interest in helping!
 
 Please create a [new issue](https://github.com/lovell/sharp/issues/new) containing the steps to reproduce the problem.
 
-If you're having installation problems, please include the output of running `npm install --verbose sharp`.
-
 New bugs are assigned a `triage` label whilst under investigation.
 
 ## Submit a new feature request
@@ -32,7 +30,6 @@ To test C++ changes, you can compile the module using `npm install --build-from-
 ## Submit a Pull Request with a new feature
 
 Please add JavaScript [unit tests](https://github.com/lovell/sharp/tree/main/test/unit) to cover your new feature.
-A test coverage report for the JavaScript code is generated in the `coverage/lcov-report` directory.
 Please also update the [TypeScript definitions](https://github.com/lovell/sharp/tree/main/lib/index.d.ts), along with the [type definition tests](https://github.com/lovell/sharp/tree/main/test/types/sharp.test-d.ts).
 
 Where possible, the functional tests use gradient-based perceptual hashes

.github/workflows/ci.yml

@@ -267,7 +267,7 @@ jobs:
             curl --silent https://${{ matrix.nodejs_hostname }}/download/release/v${{ matrix.nodejs_version}}/node-v${{ matrix.nodejs_version}}-linux-${{ matrix.nodejs_arch }}.tar.xz | tar xJC /opt/nodejs --strip-components=1
             export PATH=$PATH:/opt/nodejs/bin
             npm install --build-from-source
-            npx mocha --no-config --spec=test/unit/io.js --timeout=30000
+            node --test test/unit/io.js
             npm run package-from-local-build
       - uses: actions/upload-artifact@v4
         with: