[AL-2360] Added dataset.delete_branch() feature

[nvoxland]

🚀 🚀 Pull Request

Impact

• Bug fix (non-breaking change which fixes expected existing functionality)
• Enhancement/New feature (adds functionality without impacting existing logic)
• Breaking change (fix or feature that would cause existing functionality to change)

Description

Creates a new ds.delete_branch(branch_name) function which deletes the given branch name.

You cannot delete branches:

• You are currently on
• The main branch,
• Non-leaf branches
• That have been previously merged into another branch

Things to be aware of

• Simplified the requirements down to only "simple" branches to avoid complex history-rewriting
• It locks the version_control_info.json and the branches to delete before operating
• It takes CommitMaps referencing a branch's commits into account

Things to worry about

Is there complex version histories this doesn't handle correctly?

Additional Context

[nvoxland]

I pushed up a new version that takes CommitMap references into account and further limits what branches can be deleted to avoid logic/cleanup complexities.

Reviewers: please check the test to see if there is complex version control behaviors I'm not taking into account.