The module/nomodule tests are the most flaky ones, contributing significantly
to increase number of test failures (somewhat mitigated by auto-retries).
Fix flakiness of module/nomodule tests:
1. For module tests, increase the timeout to 5 seconds. In order for most tests
to not wait that long, change callbacks called by module scripts to verify
the results as soon as all scripts have run.
2. For nomodule tests, run the check in 1 second. All modern browsers will
need to wait that long, hence a smaller timeout, and if occasionally the
check runs too quickly, the test will still pass.
Closes gh-5699
Also, run `grunt npmcopy` to sync the "external" directory with dependencies
from package.json. For example, the Sinon library version didn't match.
Ref gh-4234
Closes gh-4297
