doc: add release note fragment on inlining changes

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 #61422.
Updates #61502.

Change-Id: Ic7f1cb7f70752446d2465ea3da6bd7488436342b
Reviewed-on: https://go-review.googlesource.com/c/go/+/549395
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>