Support setting font feature values (#11898)

Now (on `macOS` and `Windows`) we can set font feature value:
```rust
  "buffer_font_features": {
    "cv01": true,
    "cv03": 3,
    "cv09": 1,
    "VSAH": 7,
    "VSAJ": 8
  }
```

And one can still use `"cv01": true`.



https://github.com/zed-industries/zed/assets/14981363/3e3fcf4f-abdb-4d9e-a0a6-71dc24a515c2




Release Notes:

- Added font feature values, now you can set font features like `"cv01":
7`.

---------

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

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

@@ -30,14 +30,11 @@ pub fn apply_features(font: &mut Font, features: &FontFeatures) {
         let native_font = font.native_font();
         let mut feature_array =
             CFArrayCreateMutable(kCFAllocatorDefault, 0, &kCFTypeArrayCallBacks);
-        for (tag, enable) in features.tag_value_list() {
-            if !enable {
-                continue;
-            }
+        for (tag, value) in features.tag_value_list() {
             let keys = [kCTFontOpenTypeFeatureTag, kCTFontOpenTypeFeatureValue];
             let values = [
                 CFString::new(&tag).as_CFTypeRef(),
-                CFNumber::from(1).as_CFTypeRef(),
+                CFNumber::from(*value as i32).as_CFTypeRef(),
             ];
             let dict = CFDictionaryCreate(
                 kCFAllocatorDefault,