Improve support for multiple registrations of textDocument/diagnostic (#43703)

Closes https://github.com/zed-industries/zed/issues/41935

The registration ID responsible for generating each diagnostic is now
tracked. This allows us to replace only the diagnostics from the same
registration ID when a pull diagnostics report is applied.

Additionally, various deficiencies in our support for pull diagnostics
have been fixed:
- Document pulls are issued for all open buffers, not just the edited
one. A shorter debounce is used for the edited buffer. Workspace
diagnostics are also now ignored for open buffers.
- Tracking of `lastResultId` is improved.
- Stored pull diagnostics are discarded when the corresponding buffer is
closed.

Release Notes:

- Improved compatibility with language servers that use the "pull
diagnostics" feature of Language Server Protocol.

---------

Co-authored-by: Kirill Bulatov <mail4score@gmail.com>
Co-authored-by: Kirill Bulatov <kirill@zed.dev>

crates/multi_buffer/src/multi_buffer.rs

@@ -2283,6 +2283,7 @@ impl MultiBuffer {
         cx: &mut Context<Self>,
     ) {
         use language::BufferEvent;
+        let buffer_id = buffer.read(cx).remote_id();
         cx.emit(match event {
             BufferEvent::Edited => Event::Edited {
                 edited_buffer: Some(buffer),
@@ -2291,8 +2292,8 @@ impl MultiBuffer {
             BufferEvent::Saved => Event::Saved,
             BufferEvent::FileHandleChanged => Event::FileHandleChanged,
             BufferEvent::Reloaded => Event::Reloaded,
-            BufferEvent::LanguageChanged => Event::LanguageChanged(buffer.read(cx).remote_id()),
-            BufferEvent::Reparsed => Event::Reparsed(buffer.read(cx).remote_id()),
+            BufferEvent::LanguageChanged => Event::LanguageChanged(buffer_id),
+            BufferEvent::Reparsed => Event::Reparsed(buffer_id),
             BufferEvent::DiagnosticsUpdated => Event::DiagnosticsUpdated,
             BufferEvent::CapabilityChanged => {
                 self.capability = buffer.read(cx).capability();