Update git flow support to work with git-flow-next

[hmaddocks]

Lazygit has built in support for git-flow but it seems to only work with the legacy tooling and not git-glow-next. The original git-flow tooling has been deprecated in favour of git-flow-next

When I install git-flow-next and init the repo Lazygit errors out when I use "Show git flow options" command. This is because the git config format is different between the versions. I don't consider this a bug though. Instead a lack of feature.

I'd like Lazygit to work with the more recent tooling.

I have a PR ready to go with the change to make this happen but the CONTRIBUTING guidelines says I should start a discussion first.

[Melochaotic]

Also noticed this issue thank you for already working on it 😄

[Melochaotic]

This is already brought up in #4905 - no comments yet though

[hmaddocks]

Github Flow is basically feature branches. Quite different to git-flow

[hmaddocks]

Pull request here #5288