test_runner: exclude ignored branches from lcov output

[DevRajah]

Description

This updates the LCOV reporter to exclude BRDA entries for branches associated with ignored coverage lines.

Previously, ignored lines could be excluded from DA output while related branch entries were still emitted as BRDA, causing inconsistent LCOV output.

Fixes: #61586

Changes

• Skip LCOV BRDA output for ignored branch lines
• Recalculate BRF and BRH from emitted LCOV branch entries
• Add a regression test for ignored branch behavior

Testing

node test/parallel/test-runner-coverage.js


Note: I was unable to complete a full Windows source build locally because the ClangCL compile ran out of memory, but the targeted test file was run with Node.js v24.14.0.

[nodejs-github-bot]

Review requested:

• @nodejs/test_runner

[JakobJingleheimer]

Duplicate of #61598