Represent git statuses more faithfully (#23082)

First, parse the output of `git status --porcelain=v1` into a
representation that can handle the full "grammar" and doesn't lose
information.

Second, as part of pushing this throughout the codebase, expand the use
of the existing `GitSummary` type to all the places where status
propagation is in play (i.e., anywhere we're dealing with a mix of files
and directories), and get rid of the previous `GitSummary ->
GitFileStatus` conversion.

- [x] Synchronize new representation over collab
  - [x] Update zed.proto
  - [x] Update DB models
- [x] Update `GitSummary` and summarization for the new `FileStatus`
- [x] Fix all tests
  - [x] worktree
  - [x] collab
- [x] Clean up `FILE_*` constants
- [x] New collab tests to exercise syncing of complex statuses
- [x] Run it locally and make sure it looks good

Release Notes:

- N/A

---------

Co-authored-by: Mikayla <mikayla@zed.dev>
Co-authored-by: Conrad <conrad@zed.dev>

crates/tab_switcher/src/tab_switcher.rs

@@ -362,7 +362,10 @@ impl PickerDelegate for TabSwitcherDelegate {
                         .and_then(|path| {
                             let project = self.project.read(cx);
                             let entry = project.entry_for_path(path, cx)?;
-                            let git_status = project.project_path_git_status(path, cx);
+                            let git_status = project
+                                .project_path_git_status(path, cx)
+                                .map(|status| status.summary())
+                                .unwrap_or_default();
                             Some((entry, git_status))
                         })
                         .map(|(entry, git_status)| {