Event ABI Utilities

[reedsa]

What was wrong?

Related to Issue #1596, #3036

Dependent on https://github.com/ethereum/eth-utils/pull/271

Before exposing get_event_data, refactoring and cleanup is needed. A couple of utilities can be created to get log topics (as bytes) for a given event ABI.

How was it fixed?

Utilities added to handle contract event ABIs, get_event_log_topics and log_topic_to_bytes.

Todo:

• [ ] Clean up commit history
• [ ] Add or update documentation related to these changes
• [ ] Add entry to the release notes

Cute Animal Picture

[reedsa]

Merged these changes manually into #3408