chore(sequencer): consolidate all action handling to one module

[ethanoroshiba]

Summary

Moved all action and transaction handling to single module.

Background

Previously, all implementations of ActionHandler were done separately in components which corresponded to their given actions (or groups of actions, such as in bridge). While this may make sense from an action-centered point of view, it is confusing to an outsider to have to look many different places to find where stateless/stateful checks and execution occur. This PR consolidates all of the implementations as well as their testing.

Changes

• Created new action_handler module and moved the corresponding ActionHandler trait as well as all of its impls into this module.
• Renamed some moved tests for clarity.
• Categorized tests by action in submodule tests.

Testing

Passing all tests.

Changelogs

Changelogs updated

Related Issues

closes #1657