Add placeholder git panel (#21894)

Adds a simple git placeholder panel for us to iterate from. Also
includes a number of assets from the git prototyping branch that we will
use.

Note: This panel is staff flagged for now.

Release Notes:

- N/A

Cargo.lock

@@ -5169,6 +5169,17 @@ dependencies = [
  "util",
 ]
 
+[[package]]
+name = "git_ui"
+version = "0.1.0"
+dependencies = [
+ "gpui",
+ "serde",
+ "ui",
+ "windows 0.58.0",
+ "workspace",
+]
+
 [[package]]
 name = "glob"
 version = "0.3.1"
@@ -15994,6 +16005,7 @@ dependencies = [
  "futures 0.3.31",
  "git",
  "git_hosting_providers",
+ "git_ui",
  "go_to_line",
  "gpui",
  "http_client",