Rust 1.78 (#11314)

Notable things I've had to fix due to 1.78:
- Better detection of unused items
- New clippy lint (`assigning_clones`) that points out places where assignment operations with clone rhs could be replaced with more performant `clone_into`
Release Notes:

- N/A

crates/language/src/buffer.rs

@@ -2072,7 +2072,7 @@ impl Buffer {
 
     /// Override current completion triggers with the user-provided completion triggers.
     pub fn set_completion_triggers(&mut self, triggers: Vec<String>, cx: &mut ModelContext<Self>) {
-        self.completion_triggers = triggers.clone();
+        self.completion_triggers.clone_from(&triggers);
         self.completion_triggers_timestamp = self.text.lamport_clock.tick();
         self.send_operation(
             Operation::UpdateCompletionTriggers {