Code cleanups for async_track_template_result

[bdraco]

Proposed change

Code cleanups for async_track_template_result.

We no longer need to make a copy of info to last_info each execution.

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[bdraco]

In order to reduce the complexity and keep the code maintainable, I'm going to see about breaking all the listener management into a separate class after the ratelimit code is finished up in another PR.