Move p2 dependency tree logic from tycho-p2-plugin to tycho-core

[ptziegler]

This moves the algorithm which is responsible for calculating the IU dependency tree used by the dependency-tree Mojo to tycho-core, so that it can be used by other projects.

For a given project, this tree can be calculated using the P2DependencyTreeGenerator, which can be injected into a Mojo as a simple Plexus component.

[ptziegler]

Prerequisite to #3258

[laeubi]

@ptziegler can this maybe even be moved to tycho-p2-maven-plugin? or does it require any class from tycho-core that is not in tycho-api?

[ptziegler]

The "tycho-p2-maven-plugin"?

[laeubi]

The "tycho-p2-maven-plugin"?

https://github.com/eclipse-tycho/tycho/tree/main/p2-maven-plugin

[ptziegler]

Thanks. I was only looking at the projects starting with "tycho-" and completely missed that one 😅

But no, I need e.g. the TychoProjectManager to calculate the initial set of IUs that are required by a given Maven project.
While it's not strictly necessary (I could just precompute the list and then pass it as an additional argument), every method who wants to use this component would then have to effectively copy-paste the same code snippet.

[laeubi]

Right I though I have moved tychoproject to api already but it seems not the case...

[github-actions]

Test Results

  579 files  ±0    579 suites  ±0   4h 0m 33s ⏱️ + 27m 29s
  392 tests ±0    384 ✅ +1   7 💤 ±0  1 ❌  - 1 
1 176 runs  ±0  1 153 ✅ +1  22 💤 ±0  1 ❌  - 1 

For more details on these failures, see this check.

Results for commit fea2bf8. ± Comparison against base commit cf9a060.

[github-actions]

💚 All backports created successfully

Status	Branch	Result
✅	tycho-4.0.x

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