cmd/compile/internal/inline: analyze function result properties

cmd/compile/internal/inline: analyze function result properties

Add code to analyze properties of function result values, specifically
heuristics for cases where we always return allocated memory, always
return the same constant, or always return the same function.

Updates #61502.

Change-Id: I8b0a3295b5be7f7ad4c2d5b9803925aea0639376
Reviewed-on: https://go-review.googlesource.com/c/go/+/511559
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>