cmd/compile/internal: write type parameters for aliases

Writes the field for type parameter names for aliases when
the bitstream is >= V2.

This is a no-op at the moment as the writer is hardwired to V1.

Updates #68778

Change-Id: I5887e3608239b9a6a47e3cc21cacb75b84e1d186
Reviewed-on: https://go-review.googlesource.com/c/go/+/607235


Reviewed-by: David Chase <drchase@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Robert Griesemer <gri@google.com>
Reviewed-by: Cuong Manh Le <cuong.manhle.vn@gmail.com>