gpui: Introduce PlatformKeyboardLayout trait for human-friendly keyboard layout names (#29049)

This PR adds a new `PlatformKeyboardLayout` trait with two methods:
`id(&self) -> &str` and `name(&self) -> &str`. The `id()` method returns
a unique identifier for the keyboard layout, while `name()` provides a
human-readable name. This distinction is especially important on
Windows, where the `id` and `name` can be quite different. For example,
the French layout has an `id` of `0000040C`, which is not
human-readable, whereas the `name` would simply be `French`. Currently,
the existing `keyboard_layout()` method returns what's essentially the
same as `id()` in this new design.

This PR implements the `name()` method for both Windows and macOS. On
Linux, for now, `name()` still returns the same value as `id()`.

Release Notes:

- N/A

crates/gpui/Cargo.toml

@@ -66,7 +66,7 @@ x11 = [
     "x11-clipboard",
     "filedescriptor",
     "open",
-    "scap"
+    "scap",
 ]
 
 
@@ -220,6 +220,7 @@ rand.workspace = true
 windows.workspace = true
 windows-core = "0.61"
 windows-numerics = "0.2"
+windows-registry = "0.5"
 
 [dev-dependencies]
 backtrace = "0.3"