Make transition_to asynchronous by default - #4849

This PR makes transition_to asynchronous by default and adds an explicit execute_transition for synchronous transitions.

This is meant to address issues such as #4840.

The problem with these issues is that we change the execution status of the output while it is concurrently in a streaming cycle, cause inconsistent states where the output is expecting to have an encoder.

Instead, except when explicitly needed, we should wait for the next streaming cycle and execute the state change before entering it.

States changes are queued so that e.g. a reset, i.e. a stop followed by a start will still happen at once during the next streaming cycle.

Fixes: #4840

TODO

• Add regression test for Crash when output.harbor is stopped via telnet while listener is connected #4840