go/types, types2: method recv type parameter count must match base type parameter count

Check receiver type parameter count when type checking the method
signature and report a suitable error (don't rely on delayed
instantiation and possibly constraint type inference).

While at it, simplify blank name recoding and type bound rewriting.

Stop-gap measure to avoid crashes in the compiler.

Fixes #51339.
For #51343.

Change-Id: Idbe2d32d69b66573ca973339f8924b349d2bc9cc
Reviewed-on: https://go-review.googlesource.com/c/go/+/387836


Trust: Robert Griesemer <gri@golang.org>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Robert Findley <rfindley@google.com>