[release-branch.go1.17] all: merge master into release-branch.go1.17

a98589711d crypto/tls: test key type when casting
cfbd73ba33 doc/go1.17: editing pass over the "Compiler" section
ab4085ce84 runtime/pprof: call runtime.GC twice in memory profile test

Change-Id: I5b19d559629353886752e2a73ce8f37f983772df