Enable Blade on MacOS via "macos-blade" feature (#7669)

Depends on https://github.com/zed-industries/font-kit/pull/2 and
https://github.com/kvark/blade/pull/77

This change enables Blade to be also used on MacOS. It will also make it
easier to use it on Windows.

What works: most of the things. Zed loads as fast and appears equally
responsive to the current renderer.
<img width="306" alt="Screenshot 2024-02-11 at 12 09 15 AM"
src="https://github.com/zed-industries/zed/assets/107301/66d82f45-5ea2-4e2b-86c6-5b3ed333c827">

Things missing:
- [x] video streaming. ~~Requires a bit of plumbing on both Blade and
Zed sides, but all fairly straightforward.~~
  -  verified with a local setup
- [x] resize. ~~Not sure where exactly to hook up the reaction on the
window size change. Once we know where, the fix is one line.~~
- [ ] fine-tune CA Layer
- this isn't a blocker for merging the PR, but it would be a blocker if
we wanted to switch to the new path by default
- [ ] rebase on latest, get the dependency merged (need review/merge of
https://github.com/zed-industries/font-kit/pull/2!)

Update: I implemented resize support as well as "surface" rendering on
the Blade path (which will be useful on Linux/Windows later on). I
haven't tested the latter though - not sure how to get something
streaming. Would appreciate some help! I don't think this should be a
blocker to this PR, anyway.

The only little piece that's missing for the Blade on MacOS path to be
full-featured is fine-tuning the CALayer configuration. Zed does a lot
of careful logic in configuring the layer, such as switching the
"present with transaction" on/off intermittently, which Blade path
doesn't have yet.

Release Notes:
- N/A

---------

Co-authored-by: Mikayla <mikayla@zed.dev>

crates/gpui/src/platform/mac/platform.rs

@@ -52,6 +52,8 @@ use std::{
 };
 use time::UtcOffset;
 
+use super::renderer;
+
 #[allow(non_upper_case_globals)]
 const NSUTF8StringEncoding: NSUInteger = 4;
 
@@ -145,7 +147,7 @@ pub(crate) struct MacPlatformState {
     background_executor: BackgroundExecutor,
     foreground_executor: ForegroundExecutor,
     text_system: Arc<MacTextSystem>,
-    instance_buffer_pool: Arc<Mutex<Vec<metal::Buffer>>>,
+    renderer_context: renderer::Context,
     pasteboard: id,
     text_hash_pasteboard_type: id,
     metadata_pasteboard_type: id,
@@ -175,7 +177,7 @@ impl MacPlatform {
             background_executor: BackgroundExecutor::new(dispatcher.clone()),
             foreground_executor: ForegroundExecutor::new(dispatcher),
             text_system: Arc::new(MacTextSystem::new()),
-            instance_buffer_pool: Arc::default(),
+            renderer_context: renderer::Context::default(),
             pasteboard: unsafe { NSPasteboard::generalPasteboard(nil) },
             text_hash_pasteboard_type: unsafe { ns_string("zed-text-hash") },
             metadata_pasteboard_type: unsafe { ns_string("zed-metadata") },
@@ -494,12 +496,11 @@ impl Platform for MacPlatform {
         handle: AnyWindowHandle,
         options: WindowOptions,
     ) -> Box<dyn PlatformWindow> {
-        let instance_buffer_pool = self.0.lock().instance_buffer_pool.clone();
         Box::new(MacWindow::open(
             handle,
             options,
             self.foreground_executor(),
-            instance_buffer_pool,
+            self.0.lock().renderer_context.clone(),
         ))
     }