[dev.regabi] cmd/compile: rewrite stale format strings

[dev.regabi] cmd/compile: rewrite stale format strings

On ir.Node, ir.Nodes, and ir.Op, # is ignored, so %#v is %v.
On ir.Node, %S is the same as %v.

On types.Type, # is ignored, so %#L is %L, %#v is %v.
On types.Type, 0 is ignored, so %0S is %S.

Rewrite all these using go test cmd/compile -r, plus a
few multiline formats mentioning %0S on types updated by hand.

Now the formats used in the compiler match the documentation
for the format methods, a minor miracle.

Passes buildall w/ toolstash -cmp.

Change-Id: I3d4a3fae543145a68da13eede91166632c5b1ceb
Reviewed-on: https://go-review.googlesource.com/c/go/+/275782
Trust: Russ Cox <rsc@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>