keymap_ui: Auto complete action arguments (#34785)

Supersedes: #34242

Creates an `ActionArgumentsEditor` that implements the required logic to
have a JSON language server run when editing keybinds so that there is
auto-complete for action arguments.

This is the first time action argument schemas are required by
themselves rather than inlined in the keymap schema. Rather than add all
action schemas to the configuration options we send to the JSON LSP on
startup, this PR implements support for the
`vscode-json-language-server` extension to the LSP whereby the server
will request the client (Zed) to resolve URLs with URI schemes it does
not recognize, in our case `zed://`. This limits the impact on the size
of the configuration options to ~1KB as we send URLs for the language
server to resolve on demand rather than the schema itself. My
understanding is that this is how VSCode handles JSON schemas as well. I
plan to investigate converting the rest of our schema generation logic
to this method in a follow up PR.

Co-Authored-By: Cole <cole@zed.dev>

Release Notes:

- N/A *or* Added/Fixed/Improved ...

assets/keymaps/default-macos.json

@@ -1228,6 +1228,7 @@
     "context": "KeymapEditor",
     "use_key_equivalents": true,
     "bindings": {
+      "cmd-f": "search::FocusSearch",
       "cmd-alt-f": "keymap_editor::ToggleKeystrokeSearch",
       "cmd-alt-c": "keymap_editor::ToggleConflictFilter",
       "enter": "keymap_editor::EditBinding",