Update base for Update on "opcheck should be usable without optional …

…dependencies"

This PR excises opcheck's dependency on
torch.testing._internal.common_utils, (which comes with dependencies on
expecttest and hypothesis). We do this by moving what we need to
torch.testing._utils and adding a test for it.

Fixes #126870, #126871

Test Plan:
- new tests

[ghstack-poisoned]