fix(test): race condition for cancelled tests

[nayeemrmn]

Not for merging, debugging flaky test on windows fast ci
Resolves issue in #15231.

[nayeemrmn]

@dsherret I figured out where the race condition was, it was this code:

deno/cli/tools/test.rs

Line 1157 in fad8d7d

for desc in tests.read().values() {

which wrongly assumes the registration events for the relevant tests have been received, when it is only guaranteed that they have been sent. So sometimes those tests wouldn't be present in tests yet.

I've moved that behaviour to the receiving side where it belongs. Now it can be reliably checked that the sending code has no dependency on the receiver state.

[bartlomieju]

@dsherret please take a look

[dsherret]

LGTM. Thanks @nayeemrmn!