Verify that genhtml accepts the combined report

[fmeum]

This provides additional end-to-end assurance on Bazel-generated coverage.

[Copilot]

Pull Request Overview

This PR adds end-to-end validation of Bazel-generated coverage reports by verifying that genhtml can successfully process the generated LCOV files. This provides additional assurance that the coverage data format is correct and compatible with standard LCOV tooling.

Key changes:

• Added lcov as a dependency to enable genhtml validation
• Updated test files to contain actual content instead of empty files for more realistic coverage scenarios
• Added genhtml processing verification steps to coverage tests

Reviewed Changes

Copilot reviewed 4 out of 5 changed files in this pull request and generated 1 comment.

File	Description
MODULE.bazel	Added lcov dependency (v2.3.1) and reordered Maven dependencies alphabetically
src/test/shell/bazel/BUILD	Added genhtml tool as test data and configured GENHTML environment variable for all coverage test targets
src/test/shell/bazel/bazel_coverage_starlark_test.sh	Replaced empty test files with files containing actual content and added genhtml validation for coverage and baseline reports
src/test/shell/bazel/bazel_coverage_java_test.sh	Added genhtml validation step to verify coverage report can be processed

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[fmeum]

The Windows failure is due to linux-test-project/lcov#442.

[fmeum]

@c-mita CI is green now