Inline the write a glyph goes through

Whether the inliner took DrawLayers::write into Painter::glyphs turned
out to depend on unrelated code elsewhere in iris-core: adding the
declared-length resolution pushed it out, and a call per glyph cost 12%
of a resize frame with every counter -- widget draws, primitive writes,
text renders -- unchanged. Saying so directly leaves the two decisions
independent. The random-tree rig is 12.59B instructions where it was
13.25B before either change.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

core/src/primitive/layer.rs

@@ -120,6 +120,10 @@ impl<T: Default> Layers<T> {
 }
 
 impl DrawLayers {
+    /// Inlined on purpose: it is one call per glyph, the innermost thing a
+    /// frame does, and whether the inliner takes it turns out to depend on
+    /// unrelated code elsewhere in the crate -- 12% of a resize frame.
+    #[inline]
     pub fn write<P: Primitive>(
         &mut self,
         layer: LayerId,