[dev.regabi] cmd/compile: prefer types constructors over typecheck

Similar to the earlier mkbuiltin cleanup, there's a bunch of code that
calls typecheck.NewFuncType or typecheck.NewStructType, which can now
just call types.NewSignature and types.NewStruct, respectively.

Passes toolstash -cmp.

Change-Id: Ie6e09f1a7efef84b9a2bb5daa7087a6879979668
Reviewed-on: https://go-review.googlesource.com/c/go/+/279955


Trust: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>