Add a separate Branch Permissions to prevent Branch Creation

Problem Definition

The "Prevent Changes without a Pull Request" branch permission allows branches to be created through the UI by all users.
The "Prevent All Changes" branch permissions prevent pull requests from being merged.

There should be a way to prevent new branches from being created in the UI while still allowing pull requests for existing branches to be merged.

Suggested Solution

Add "Prevent new branches" to the existing list of Branch Permission options.

Why this is important

This allows tighter control of how many branches are allowed in a repository.

Workaround

None at this time.