* Miscellaneous SourceManager updates
* Own the chunks channel instead of accepting it as an input
* Add Chunks and Wait methods
* Fix bug in Enroll so it actually returns the handle
* Add context.Context parameter to the SourceInitFunc type
* Add SourceManager tests for Run and Wait methods
* Rename man variables to mgr
* Implement SourceManager basics
* Rename identifiers and add a default headlessAPI implementation
* Rewrite to use SourceInitFunc
* Update variable name to accurately reflect its value