[consensus] rename event_processor test to better reflect the purpose
[consensus] rename event_processor test to better reflect the purpose

We test the expected behavior upon certain events, rename the tests to
be [expected_behavior]_on_[certain_events].

Add a few new tests.

Closes: #3488
Approved by: davidiw

libra/libra,libra/libra,libra/libra,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core,libra/libra,aptos-labs/aptos-core,aptos-labs/aptos-core,aptos-labs/aptos-core