Replace cgroups v2 uncross agent tests

[kanderson250]

Our file-reading tests for getting the docker container id with cgroups v2 were written before the cross agent tests for this feature were added. The cross agent tests now exist and should be used instead.

Remove the cgroups v2 test files from the uncross_agent_tests, and redirect the DockerDataTest to read the test files from the cross_agent_tests.

This should amount to deleting the cgroups v2 directory in uncross_agent_test and updating the filepath and files in DockerDataTest.

[workato-integration]

https://new-relic.atlassian.net/browse/NR-279831