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>

script/zed-local

@@ -21,6 +21,7 @@ OPTIONS
   -2, -3, -4, ...   Spawn multiple Zed instances, with their windows tiled.
   --top             Arrange the Zed windows so they take up the top half of the screen.
   --stable          Use stable Zed release installed on local machine for all instances (except for the first one).
+  --preview         Like --stable, but uses the locally-installed preview release instead.
 `.trim();
 
 const { spawn, execSync, execFileSync } = require("child_process");
@@ -48,6 +49,7 @@ let instanceCount = 1;
 let isReleaseMode = false;
 let isTop = false;
 let othersOnStable = false;
+let othersOnPreview = false;
 let isStateful = false;
 
 const args = process.argv.slice(2);
@@ -68,6 +70,8 @@ while (args.length > 0) {
     process.exit(0);
   } else if (arg === "--stable") {
     othersOnStable = true;
+  } else if (arg === "--preview") {
+    othersOnPreview = true;
   } else {
     break;
   }
@@ -172,6 +176,8 @@ setTimeout(() => {
     let binaryPath = zedBinary;
     if (i != 0 && othersOnStable) {
       binaryPath = "/Applications/Zed.app/Contents/MacOS/zed";
+    } else if (i != 0 && othersOnPreview) {
+      binaryPath = "/Applications/Zed Preview.app/Contents/MacOS/zed";
     }
     spawn(binaryPath, i == 0 ? args : [], {
       stdio: "inherit",