There were some failures in the Crl Directory related tests after https://github.com/grpc/grpc/pull/36031
This came down to https://github.com/grpc/grpc/pull/36031 adding some CRLs with bad qualities (invalid content/signatures, overriding issuer names) to the `test_creds/crl_data/crls` directory, which is used in the directory reloading tests. The tests began failing on some platforms because they were picking up these bad crls which were failing various checks, but the test was designed to assume that `test_creds/crl_data/crls` was a valid and good directory.
This PR moves the bad CRLs to their own directory to prevent this accidental mash-up of test data. It also adds debug logging to our custom verification stack.
Closes#36122