doc: add release note fragment on inlining changes

Add some material to the "compiler" portion of the release
notes describing the 1.22 changes to the inliner.

For golang#61422.
Updates golang#61502.

Change-Id: Ic7f1cb7f70752446d2465ea3da6bd7488436342b
Reviewed-on: https://go-review.googlesource.com/c/go/+/549395
Reviewed-by: David Chase <[email protected]>
Reviewed-by: Matthew Dempsky <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>

Author: thanm

doc/go1.22.html

@@ -219,6 +219,18 @@ <h2 id="compiler">Compiler</h2>
   14% improvement from enabling PGO.
 </p>
 
+<p><!-- https://go.dev/cl/528321 -->
+  The compiler now interleaves devirtualization and inlining, so interface
+  method calls are better optimized.
+</p>
+
+<p><!-- https://go.dev/issue/61502 -->
+  Go 1.22 also includes a preview of an enhanced implementation of the compiler's inlining phase that uses heuristics to boost inlinability at call sites deemed "important" (for example, in loops) and discourage inlining at call sites deemed "unimportant" (for example, on panic paths).
+  Building with <code>GOEXPERIMENT=newinliner</code> enables the new call-site
+  heuristics; see <a href="https://go.dev/issue/61502">issue #61502</a> for
+  more info and to provide feedback.
+</p>
+
 <h2 id="linker">Linker</h2>
 
 <p><!-- CL 493136 -->