runtime: repair gdb printing fix for 7.12, 8.{1,2,3}.1, 9.2
Hand-verified for listed gdb versions. Gdb (apparently)
changed the way it names certain Go types, and this change
broke the pretty-printer-activating code in runtime-gdb.py
runtime-gdb_test.go now checks channel, map, string, and slice
printing unconditionally (i.e., no opt-out for old versions).
Updates #39368.
Change-Id: I98d72e1291c66bd40d970990e1a377ff2ed0c5d2
Reviewed-on: https://go-review.googlesource.com/c/go/+/236164
Run-TryBot: David Chase <drchase@google.com> Reviewed-by: Than McIntosh <thanm@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>