hash/maphash: add WriteComparable and Comparable
Default, use hash function in the runtime package.
If the build tag is purego or raw memory cannot be hash directly,
use reflect get each field to hash separately.
Fixes #54670
Change-Id: Ic968864c9c3c51883967d4f6dc24432385c7dc79
GitHub-Last-Rev:
5ae8a28834c8b809a52c74617e2a8530acec8095
GitHub-Pull-Request: golang/go#69166
Reviewed-on: https://go-review.googlesource.com/c/go/+/609761
Reviewed-by: Keith Randall <khr@google.com>
Reviewed-by: Keith Randall <khr@golang.org>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: David Chase <drchase@google.com>