Moving coverage, xunit, pytest installation to Docker (#47082)
Summary:
Fixes a TODO. This PR moves `pip_install unittest-xml-reporting coverage pytest` to the base Ubuntu docker instead of running that installation during every test.
This should save some time.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/47082
Reviewed By: samestep
Differential Revision: D24634393
Pulled By: janeyx99
fbshipit-source-id: 3b980890409eafef9b006b9e03ad7f3e9017529e
