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/collab/migrations/20250113230049_expand_git_status_information.sql

@@ -0,0 +1,13 @@
+ALTER TABLE worktree_repository_statuses
+ADD COLUMN status_kind INTEGER,
+ADD COLUMN first_status INTEGER,
+ADD COLUMN second_status INTEGER;
+
+UPDATE worktree_repository_statuses
+SET
+    status_kind = 0;
+
+ALTER TABLE worktree_repository_statuses
+ALTER COLUMN status_kind
+SET
+    NOT NULL;