cmd/compile: remove reflectdata.AfterGlobalEscapeAnalysis

cmd/compile: remove reflectdata.AfterGlobalEscapeAnalysis

This global variable was used by the old frontend to decide whether to
perform escape analysis during method wrapper generation.

The old frontend is gone now, the variable is not used anywhere else.

Change-Id: I448f2761ea608a9a2ec39a9920fcf7aa12d98799
Reviewed-on: https://go-review.googlesource.com/c/go/+/466278
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Keith Randall <khr@google.com>
Auto-Submit: Cuong Manh Le <cuong.manhle.vn@gmail.com>
TryBot-Result: Gopher Robot <gobot@golang.org>