HDDS-15566. Move feature branch merge checklist to the website

[errose28]

What changes were proposed in this pull request?

Move the feature branch merge checklist from confluence to the new website. As part of this change:

• The checklist was updated
• Docs on the project's git usage were rearranged to make room for the new content
• All existing branch merge checklists from confluence were reformatted to markdown by AI and imported here
• A process to raise new branch merge checklists as PRs to this repo for review is proposed

What is the link to the Apache Jira?

HDDS-15566

How was this patch tested?

Local preview

[errose28]

@gardenia This is the switch of the branch merge checklist to the new website I mentioned at the community sync.

[errose28]

We need to decide what our actual guidelines are for:

1. Updating feature branches with changes from master incrementally
2. Incorporating the feature branch back into master

We want to avoid using merge for 1 and 2, because the layers of merge commits become difficult to follow when tracking the git history.

One option is using rebase to bring the commits into master. That will erase any merge commits on the branch so devs are free to use either rebase or merge to update their feature branch from master while working.

Another option is to rebase the feature branch and then merge it to master. This way master doesn't need to stay frozen while the feature branch rebase is happening. We may want to force a merge commit in this case even if it is not necessary for consistency across feature branch merges.

If there is another way to scrub the incremental merge commits before merging to master we could use that as well.