Add Eclipse release compatibility matrix workflow and parameterized target-platform resolution

[Copilot]

This PR adds a dedicated compatibility CI path to verify the plugin against Eclipse releases from 2024-06 through 2026-03 without editing source configuration per run. It introduces target-platform indirection and Tycho property switches so one build config can validate multiple Eclipse baselines.

• Compatibility matrix workflow

  • Added .github/workflows/compatibility.yml with an 8-version Eclipse matrix (2024-06 … 2026-03).
  • Uses quoted Maven -D... arguments to avoid Windows PowerShell argument-splitting issues.
  • Applies per-target EE-constraint behavior in matrix runs (true for 2024-*, false for 2025-03+).

• Versioned target platform definitions

  • Added targets/*.target for:
    • 2024-06, 2024-09, 2024-12, 2025-03, 2025-06, 2025-09, 2025-12, 2026-03.
  • Each target file keeps dependency units aligned with the current project target definition while switching only the Eclipse release repository URL.

• Default baseline target indirection

  • Updated target-platform.target to include targets/2024-06.target via a nested <location type="Target" .../>.
  • Keeps baseline definition centralized while enabling matrix overrides.

• Tycho/Maven parameterization

  • Updated root pom.xml to introduce:
    • target.platform.file (default: target-platform.target)
    • target.resolve.with.ee.constraints (default: true)
  • Wired these into target-platform-configuration so CI can select target and EE-resolution mode by properties.

Example matrix build invocation now used in workflow:

run: mvn -B clean verify -ntp "-Dtarget.platform.file=targets/${{ matrix.target }}.target" "-Dtarget.resolve.with.ee.constraints=${{ startsWith(matrix.target, '2024-') && 'true' || 'false' }}"