replace TimeManager with CallbackManager module

[juliasloan25]

Purpose

Rename TimeManager module to CallbackManager, and add some functions needed by ClimaCoupler.

To-do

• rename
• add new functions to src and docs
• generalize trigger_callback! - dispatch on callback type
• check that dt_cb is being used correctly
• add tests (get from coupler ?)
• extend docs, add examples for usage

Content

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