Give users more control over command args

**Is your feature request related to a problem? Please describe.**
Lazygit currently runs some git commands with arguments applied that we consider to be sensible defaults. But different situations call for different args and users need a way of controlling the flags that are used.

**Describe the solution you'd like**
I don't have a good solution for this worked out in my head. We could learn a lot from observing how magit goes about this, but I haven't dug into that myself enough to know how much we want to emulate it. I want lazygit's main focus to be about making _typical_ actions easy and fast, so if every action now costs an extra keybinding because we have to show a separate menu when they can configure command args, that's not worth it.

But I suspect there is a sensible middleground we can find.

Part of the solution will be to extend the functionality of our menus so that you can toggle flags / cycle options using keybindings associated with those options. Currently our menus only support selecting a single item and invoking it.

**Describe alternatives you've considered**
Luckily, custom commands can fill most of the current gap, with the caveat being that they can't be configured at runtime and that we don't have a menu view that supports toggling flags or cycling through a bunch of options.