E2E open-sourced

[rnugmanx]

[github-actions[bot]]

This PR will be closed in a week because of 2 weeks of no activity.

[rnugmanx]

Removed readme in pipelines folder, remaining readme in help_scripts and readme in the root folder have different customers so I left it as is. Also I added info about how to add test for model from tf hub repo. For possible options there is 'pytest test.py -h' option which is already described in readme. Removed some redundant info from readme regarding advanced entrypoints

Structure of e2e tests now: e2e |-----test_utils |-----common |-----pipelines |--------tensorflow |--------pytorch (will be added later) |-----run_tests.py # common entry point

[rkazants]

@ilya-lavrenov, let us merge cleaned up version.