cmd/compile: use equality signatures in hash function generation
There aren't a huge number of generated hash functions, so this probably
won't save a whole lot of memory. But it means we can clean up a bunch
of code by basing equality and hashing on the same underlying infrastructure.
Change-Id: I36ed1e49044fecb33120d8736f1c0403a4a2554e
Reviewed-on: https://go-review.googlesource.com/c/go/+/727500 Reviewed-by: Keith Randall <khr@google.com> Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com> Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>