[dev.typeparams] merge: merge branch 'dev.regabi' into 'dev.typeparams'

The following files had merge conflicts and were merged manually:

	src/cmd/compile/fmtmap_test.go
	src/cmd/compile/internal/gc/noder.go
	src/go/parser/error_test.go
	test/assign.go
	test/chan/perm.go
	test/fixedbugs/issue22822.go
	test/fixedbugs/issue4458.go
	test/init.go
	test/interface/explicit.go
	test/map1.go
	test/method2.go

The following files had manual changes to make tests pass:

	test/run.go
	test/used.go
	src/cmd/compile/internal/types2/stdlib_test.go

Change-Id: Ia495aaaa80ce321ee4ec2a9105780fbe913dbd4c