Introduce isLatest flag to mark latest version of project

[rkg-mm]

Current Behavior

Currently, Dependency-Track has no idea which version is the latest. Version numbers follow different formats, so figuring this out automatically is difficult, as no solution will fit everyone.
Some users try to get around this, by labelling latest versions with tags. However, having this information in a standardized format would be much more beneficial:

1. Other features (e.g. collection logic, see Introduce "collection" projects for better usage of hierarchical view #2041  #3258) could make use of it. In future possibly also rules could be applied only to latest versions (e.g. outdated dependency rules, which make no sense on older versions)
2. The system could automate the update of this flag, not relying on client scripts to update the "old" latest project to remove the tag and add it to the newest version. This causes additional client scripting effort and can fail, leaving it in inconsistent state.

Proposed Behavior

Based on discussion with @nscuro in #3258 there should be a flag "isLatest" introduced, which marks a project as latest version.
When this is set to TRUE on a project, the flag automatically is reset to FALSE on all other versions of this project.
This can be enforced with UNIQUE constraint on (NAME, IS_LATEST).

Hint:
If #3258 is merged already, the preparation for Collection logic LATEST_VERSION_CHILDREN in ProjectMetricsUpdateTask.updateLatestVersionChildrenCollectionMetrics() should be activated during implementation of this feature.

Checklist

• I have read and understand the contributing guidelines
• I have checked the existing issues for whether this enhancement was already requested

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