all: use ocimem in its immutable form in all tests
Unfortunately, ocimem.New defaults to a mutable in-memory registry,
which hides any unintended mutations in our tests
as we should be trying to mimic a realistic immutable registry setup.
The only exception is a modregistry client test
which does expect to be able to delete a tag, but that one is fine.
Raised https://github.com/cue-labs/oci/issues/33 to track making
ocimem.New default to an immutable registry, and opting into mutability.
Signed-off-by: Daniel Martí <mvdan@mvdan.cc>
Change-Id: I0368f075455640e360601b047cfb62b86e3b064c
Reviewed-on: https://review.gerrithub.io/c/cue-lang/cue/+/1195730
Reviewed-by: Paul Jolly <paul@myitcv.io>
TryBot-Result: CUEcueckoo <cueckoo@cuelang.org>