refactor: expose bundle source paths in execroot form

[AlexanderLanin]

What this achieves

Passes an execution-root-relative source path from bundle analysis directly to Needs generation.

Why this is needed

Bundle analysis already knows both the runtime and execution-root spellings. Keeping the execution-root path in the provider makes that contract explicit and removes duplicate path conversion from the Needs rule.

Changes

• Rename the provider field own_source_root to source_dir_execroot_path.
• Compute the execution-root path once in the bundle rule and reuse it for the manifest and provider.
• Make needs_rules.bzl consume the provider path directly.

[github-actions]

Documentation preview for this pull request is available at:
pr-824: https://eclipse-score.github.io/docs-as-code/pr-824/

[MaximilianSoerenPollak]

Having these stacked PR'' s makes this much easier to review I gotta admit.

Although coudl also be because these changes are small in themselfs.