Simplify TextHighlights map (#21724)

Remove unnecessary `Option` wrapping.

crates/editor/src/display_map/inlay_map.rs

@@ -211,7 +211,7 @@ pub struct InlayBufferRows<'a> {
 struct HighlightEndpoint {
     offset: InlayOffset,
     is_start: bool,
-    tag: Option<TypeId>,
+    tag: TypeId,
     style: HighlightStyle,
 }
 
@@ -239,7 +239,7 @@ pub struct InlayChunks<'a> {
     max_output_offset: InlayOffset,
     highlight_styles: HighlightStyles,
     highlight_endpoints: Peekable<vec::IntoIter<HighlightEndpoint>>,
-    active_highlights: BTreeMap<Option<TypeId>, HighlightStyle>,
+    active_highlights: BTreeMap<TypeId, HighlightStyle>,
     highlights: Highlights<'a>,
     snapshot: &'a InlaySnapshot,
 }
@@ -1096,7 +1096,7 @@ impl InlaySnapshot {
         &self,
         cursor: &mut Cursor<'_, Transform, (InlayOffset, usize)>,
         range: &Range<InlayOffset>,
-        text_highlights: &TreeMap<Option<TypeId>, Arc<(HighlightStyle, Vec<Range<Anchor>>)>>,
+        text_highlights: &TreeMap<TypeId, Arc<(HighlightStyle, Vec<Range<Anchor>>)>>,
         highlight_endpoints: &mut Vec<HighlightEndpoint>,
     ) {
         while cursor.start().0 < range.end {
@@ -1112,7 +1112,7 @@ impl InlaySnapshot {
                     )))
                 };
 
-            for (tag, text_highlights) in text_highlights.iter() {
+            for (&tag, text_highlights) in text_highlights.iter() {
                 let style = text_highlights.0;
                 let ranges = &text_highlights.1;
 
@@ -1134,13 +1134,13 @@ impl InlaySnapshot {
                     highlight_endpoints.push(HighlightEndpoint {
                         offset: self.to_inlay_offset(range.start.to_offset(&self.buffer)),
                         is_start: true,
-                        tag: *tag,
+                        tag,
                         style,
                     });
                     highlight_endpoints.push(HighlightEndpoint {
                         offset: self.to_inlay_offset(range.end.to_offset(&self.buffer)),
                         is_start: false,
-                        tag: *tag,
+                        tag,
                         style,
                     });
                 }
@@ -1708,7 +1708,7 @@ mod tests {
             text_highlight_ranges.sort_by_key(|range| (range.start, Reverse(range.end)));
             log::info!("highlighting text ranges {text_highlight_ranges:?}");
             text_highlights.insert(
-                Some(TypeId::of::<()>()),
+                TypeId::of::<()>(),
                 Arc::new((
                     HighlightStyle::default(),
                     text_highlight_ranges