cmd/cgo: walk {FuncType,TypeSpec}.TypeParams fields
This CL updates the cgo tool to walk the TypeParams fields for
function types and type declarations, so that C.xxx identifiers can
appear within type parameter lists.
Fixes #52542.
Change-Id: Id02a88d529d50fe59b0a834f415c2575204ffd1f
Reviewed-on: https://go-review.googlesource.com/c/go/+/453977
Run-TryBot: Matthew Dempsky <mdempsky@google.com> Reviewed-by: Ian Lance Taylor <iant@google.com>
Auto-Submit: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>