This is a first step in refactoring abc_p2p_avalanche.py, because it is testing too many things. The avalanche enabled P2PInterface used in this file will be reused in multiple tests after this is split up into smaller pieces.
This commit does the following:
- move `abc_p2p_avalanche.TestNode` to `test_framework.avatools.AvaP2PInterface`
- move `get_node` (previously defined locally in run_tests) to avatools.py and rename it `get_ava_p2p_interface`
- add an `AvaP2PInterface.setNodeId` method instead of monkey-patching the object after instantiation. This is a request from the `mypy` linter, which raised an error because "AvaP2PInterface has no attribute nodeid" when assigning a nodeid in `get_ava_p2p_interface`
Except for the renaming and new method, no code is changed. It does not change the behavior.