Add a live Rust style editor to inspector to edit a sequence of no-argument style modifiers (#31443)

Editing JSON styles is not very helpful for bringing style changes back
to the actual code. This PR adds a buffer that pretends to be Rust,
applying any style attribute identifiers it finds. Also supports
completions with display of documentation. The effect of the currently
selected completion is previewed. Warning diagnostics appear on any
unrecognized identifier.


https://github.com/user-attachments/assets/af39ff0a-26a5-4835-a052-d8f642b2080c

Adds a `#[derive_inspector_reflection]` macro which allows these methods
to be enumerated and called by their name. The macro code changes were
95% generated by Zed Agent + Opus 4.

Release Notes:

* Added an element inspector for development. On debug builds,
`dev::ToggleInspector` will open a pane allowing inspecting of element
info and modifying styles.

assets/keymaps/default-linux.json

@@ -676,6 +676,7 @@
   {
     "bindings": {
       "ctrl-alt-shift-f": "workspace::FollowNextCollaborator",
+      // Only available in debug builds: opens an element inspector for development.
       "ctrl-alt-i": "dev::ToggleInspector"
     }
   },

assets/keymaps/default-macos.json

@@ -736,6 +736,7 @@
       "ctrl-alt-cmd-f": "workspace::FollowNextCollaborator",
       // TODO: Move this to a dock open action
       "cmd-shift-c": "collab_panel::ToggleFocus",
+      // Only available in debug builds: opens an element inspector for development.
       "cmd-alt-i": "dev::ToggleInspector"
     }
   },