What does this PR do?

This PR transitions the extraction of library test parameters from a GitHub Actions Bash step into a dedicated Gradle task and introduces stricter semantic validation for library indexes.

1. New extractLibraryTestParams Gradle Task

Moved the logic for resolving test paths and versions from unmaintained shell scripts into a formal Gradle task.

• Authority-Based Resolution: Fixed a bug where the workflow previously ignored the "latest": true flag and the "test-version" overrides in index.json. Previously, the system relied on a simple filesystem directory scan, which could lead to incorrect version selection.
• Source of Truth: The task now treats index.json as the primary authority. It resolves versions in the following priority:
  1. The entry explicitly marked "latest": true.
  2. The entry with the highest "metadata-version" defined in the JSON.
  3. (Fallback) The highest version directory found on the filesystem.
• CI Integration: Centralizes the resolution of LATEST_VERSION, TEST_PATH, and TEST_COORDINATES, automatically populating GITHUB_ENV when run in CI.

2. Enhanced Semantic Index Validation

Updated the validateIndexFiles task with a new "Forward-Referencing" integrity check.

• The Rule: In any index.json, a version in the tested-versions array cannot be higher than the next available metadata-version in the same file.
• The Problem: This prevents logical inconsistencies where an older metadata entry mistakenly "claims" library versions that actually belong to a newer metadata entry.

Fixes: #914