Refactor navigator testing

[ssbarnea]

Testing on navigator must be refactored in such way that it will address the following:

• tests can be run on and pass on both supported platforms
• regenerating fixtures would not produce different dumps on different machines
• we can test multiple versions of ansible
• we can also test ansible-devel (unpinned dependencies!)
• we would not need different fixtures for each version of ansible
• the need to regenerate fixtures would be minimized
• each test must be atomic, and we should be able to run a single test (not a single test file!). The multi step tests are not multiple tests, are in fact just more complex single tests. As a developer, if I do pytest --collect-only I should be able to pick any listed test and run it.
• Add implicit exports into __init__.py tmux-python/libtmux#531