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>

docs/src/configuring_zed.md

@@ -383,7 +383,9 @@ To override settings for a language, add an entry for that language server's nam
   "enabled": false,
   "show_type_hints": true,
   "show_parameter_hints": true,
-  "show_other_hints": true
+  "show_other_hints": true,
+  "edit_debounce_ms": 700,
+  "scroll_debounce_ms": 50
 }
 ```
 
@@ -402,6 +404,9 @@ The following languages have inlay hints preconfigured by Zed:
 
 Use the `lsp` section for the server configuration. Examples are provided in the corresponding language documentation.
 
+Hints are not instantly queried in Zed, two kinds of debounces are used, either may be set to 0 to be disabled.
+Settings-related hint updates are not debounced.
+
 ## Journal
 
 - Description: Configuration for the journal.