Allow rebase custom patch options for subcommits-started patch if from current branch

### Is your feature request related to a problem? Please describe.
I was really confused as to why sometimes after creating a custom patch, the custom patch options menu would be missing some options like "Remove patch from original commit" or "Move patch out into index" even though they should be possible.

After playing around some more and looking at the code, it turns out this was due to my inconsistent muscle memory sometimes starting the custom patch from the branches -> subcommits view of the currently checked-out branch vs directly from the commits panel.

### Describe the solution you'd like
I don't think this discrepancy should exist. The two views are essentially semantically identical when drilling down on the current branch and all the rebase-related operations work in one versus the other.

### Describe alternatives you've considered
N/A

### Additional context
This was originally opened as a PR: https://github.com/jesseduffield/lazygit/pull/5801. Only after creating it did I see lazygit's contribution policy changed recently. Feel free to close/use that PR.

Compare custom patch option handling when started from the current branch's branches -> subcommits view with the commits panel, using the behavior described in the issue and the referenced PR as the starting point. The work is done when both semantically equivalent entry points expose the same applicable rebase options, including removing a patch from its original commit and moving it into the index.

Written by the indexing model from the issue text.