Delete many branches locally

[waelmahrous]

• PR Description
  This PR will allow the user to delete multiple branches at the same time. See Delete Multiple Branches #4041.
• Please check if the PR fulfills these requirements

• Cheatsheets are up-to-date (run go generate ./...)
• Code has been formatted (see here)
• Tests have been added/updated (see here for the integration test guide)
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[rafgugi]

IMO introducing a new "RemoveMany" command might not be strictly useful. I think we should also enable deleting multiple branches using multi-select

[jesseduffield]

I agree: there's no need for a new keybinding here; we just need to do something different if the user presses the usual 'remove' key when multiple branches are selected

[stefanhaller]

I agree as well, but it's not easy at all (the "just" in your comment suggests that it might be).

The bespoke extra command that's added in this PR deletes only local branches; this is easy to do, and if it's an extra command, it could be justifiable if the command name and tooltip makes this very clear (which this PR doesn't). However, if we include the multi-select functionality in the normal delete menu, then I'd expect this to work the same as for a single selection:

• it should offer to delete only the local branches, or only the remote branches, or both (the latter two should be disabled if not all of the selected branches have upstream branches)
• it should prompt for confirmation if some of the local branches aren't fully merged

As an intermediate solution that might be good enough for now, and will be a lot easier, we could simply disable the remoteDeleteItem and deleteBothItem in case there's a multiselection, with a DisabledReason saying that this is not supported for multiselections.

[stefanhaller]

Ok, turns out that it's not that hard (sometimes you have to try it to find out). Here's a PR: #4073

Basically, the main change is that whenever we make a decision, we replace that with either lo.Every or lo.Some on the selected branches. The most tricky part was deleting several remote branches: we have to group them by remote and then loop over the remotes and issue one push --delete call with the selected branches for that remote.