editor: Shrink size of Inlay slightly (#39089)

And some other smaller cleanup things I noticed while reading through
some stuff

Release Notes:

- N/A *or* Added/Fixed/Improved ...

crates/multi_buffer/src/multi_buffer.rs

@@ -54,7 +54,7 @@ use util::post_inc;
 const NEWLINES: &[u8] = &[b'\n'; u8::MAX as usize];
 
 #[derive(Debug, Default, Clone, Copy, Hash, PartialEq, Eq, PartialOrd, Ord)]
-pub struct ExcerptId(usize);
+pub struct ExcerptId(u32);
 
 /// One or more [`Buffers`](Buffer) being edited in a single view.
 ///
@@ -7202,7 +7202,7 @@ impl ExcerptId {
     }
 
     pub fn max() -> Self {
-        Self(usize::MAX)
+        Self(u32::MAX)
     }
 
     pub fn to_proto(self) -> u64 {
@@ -7222,7 +7222,7 @@ impl ExcerptId {
 
 impl From<ExcerptId> for usize {
     fn from(val: ExcerptId) -> Self {
-        val.0
+        val.0 as usize
     }
 }