Debounce refresh of inlay hints on buffer edits (#8282)

I think this makes it less chaotic to edit text when the inlay hints are
on.

It's for cases where you're editing to the right side of an inlay hint.
Example:

```rust
for name in names.iter().map(|item| item.len()) {
    println!("{:?}", name);
}
```

We display a `usize` inlay hint right next to `name`.

But as soon as you remove that `.` in `names.iter` your cursor jumps
around because the inlay hint has been removed.

With this change we now have a 700ms debounce before we update the inlay
hints.

VS Code seems to have an even longer debounce, I think somewhere around
~1s.

Release Notes:

- Added debouncing to make it easier to edit text when inlay hints are
enabled and to save rendering of inlay hints when scrolling. Both
debounce durations can be configured with `{"inlay_hints":
{"edit_debounce_ms": 700}}` (default) and `{"inlay_hints":
{"scroll_debounce_ms": 50}}`. Set a value to `0` to turn off the
debouncing.


### Before


https://github.com/zed-industries/zed/assets/1185253/3afbe548-dcfb-45a3-ab9f-cce14c04a148



### After



https://github.com/zed-industries/zed/assets/1185253/7ea90e42-bca6-4f6c-995e-83324669ab43

---------

Co-authored-by: Kirill <kirill@zed.dev>

crates/language/src/language_settings.rs

@@ -327,12 +327,34 @@ pub struct InlayHintSettings {
     /// Default: true
     #[serde(default = "default_true")]
     pub show_other_hints: bool,
+    /// Whether or not to debounce inlay hints updates after buffer edits.
+    ///
+    /// Set to 0 to disable debouncing.
+    ///
+    /// Default: 700
+    #[serde(default = "edit_debounce_ms")]
+    pub edit_debounce_ms: u64,
+    /// Whether or not to debounce inlay hints updates after buffer scrolls.
+    ///
+    /// Set to 0 to disable debouncing.
+    ///
+    /// Default: 50
+    #[serde(default = "scroll_debounce_ms")]
+    pub scroll_debounce_ms: u64,
 }
 
 fn default_true() -> bool {
     true
 }
 
+fn edit_debounce_ms() -> u64 {
+    700
+}
+
+fn scroll_debounce_ms() -> u64 {
+    50
+}
+
 impl InlayHintSettings {
     /// Returns the kinds of inlay hints that are enabled based on the settings.
     pub fn enabled_inlay_hint_kinds(&self) -> HashSet<Option<InlayHintKind>> {