Replace git2 with gix

[Canop]

git2 is a problem mainly due to its usage of glibc and induced compilation problems.

So the goal would be to try replacing git2 with gix and check performances are OK.

[Canop]

git2 usages in broot:

1. Find the location of the global .gitignore file. This should be possible with the Repository.path_by_key function of gix

2. Get a summary (added lines/removed lines) of the changes in the worktree: solution with gix to be determined

3. Get the git status of a path (i.e. the equivalent of git2's Status). This isn't currently possible in gix, blocked by gix-worktree and gix-index (checkout, status, commit) GitoxideLabs/gitoxide#301

[Canop]

Note: if somebody has a 100% Rust reliable solution to get path status without gix, please suggest.

[Canop]

Progress: https://github.com/Canop/stagix

I'm only missing the numbers of lines added/removed