[TARS1] Refactor to async-like syntax for a linear implementation

Previosly the TARS1 refueling procedure was implemented as various
explicit switch-case statements, with various events being manually
posted to the event queue, which was somewhat hard to read and reason
about.
This commit introduces 'ASYNC_' macros that allow async-like syntax to
be used for waiting on delayed events, allowing a linear implementation
of the code as if it was synchronous.
If these are proven to be useful and work well, we might consider adding
them to the FSM base class.