runtime, testing/synctest: verify cleanups/finalizers run outside bubbles
Cleanup functions and finalizers must not run in a synctest bubble.
If they did, a function run by the GC at an unpredictable time
could unblock a bubble that synctest believes is durably
blocked.
Add a test verifying that cleanups and finalizers are always
run by non-bubbled goroutines. (This is already the case because
we never add system goroutines to a bubble.)
For #67434
Change-Id: I5a48db2b26f9712c3b0dc1f425d99814031a2fc1
Reviewed-on: https://go-review.googlesource.com/c/go/+/675257 Reviewed-by: Michael Pratt <mpratt@google.com>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Damien Neil <dneil@google.com>