feat(lsp): support test coverage visualization

[dmthong181096]

/claim #18147

Description

This pull request implements native test coverage visualization in Deno's LSP by adding support for the custom deno/testCoverage notification (resolves #18147). This allows editor extensions (such as the Deno VS Code extension) to render line coverage gutters.

Key Changes

1. LSP Customs & Client: Added TestCoverageNotification types and routing in the client notification dispatcher.
2. Deno Coverage Tools: Refactored the core parsing logic of the coverage tool into collect_coverage_reports to allow programmatic in-memory collection of results (retaining accurate sourcemap translations to original TypeScript source lines).
3. LSP Execution: Modified the test run execution flow to collect coverage raw profiles into a temporary directory during kind: "coverage" runs, parse them asynchronously, and dispatch the line hit counts to the editor.
4. Integration Tests: Added lsp_testing_api_coverage in tests/integration/lsp_tests.rs to verify that executing tests with the coverage option correctly emits notifications containing line coverage hit counts.

Verification

• Verified by running the integration test suite:

  cargo test -p integration_tests lsp_testing_api

[deno-cla-assistant]

Deno Individual Contributor License Agreement

All contributors have signed the CLA. Thank you!

• @dmthong181096

Re-run CLA check

---

This is an automated message from CLA Assistant

[dmthong181096]

/try