This is slightly more efficient and removes explicit dependence
on string layout and alignment. Build tags control use.
Because of what is arguably a bug in go 1.20's treatment of build tags,
is build-tagged to go1.21, not go1.20. (1.20 sees that it matches the
build tag and tries to compile the file, but then demands that it only use
language features from the version mentioned in go.mod. Go 1.21 and 1.22
behave more sensibly.)
Change-Id: I0cfc3b2e5651595edd3a82d9071d918700f961cd
Reviewed-on: https://go-review.googlesource.com/c/protobuf/+/545195
Reviewed-by: Cassondra Foesch <cfoesch@gmail.com>
Run-TryBot: David Chase <drchase@google.com>
Reviewed-by: Lasse Folger <lassefolger@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
