Remove half/full sync sequential decision from decoders

[DeionSi]

This change replaces hasSync and BIT_STATUS3_HALFSYNC for all purposes except communications. Instead the decoders sets the decoderSync variable to the current decoded resolution. This way the decoders does not have to care about the sequential or not operation of Speeduino.

Firmware size, memory used and performance are unaffected. Bench-tested on mega with a few decoders.

[TBAMax]

I looked briefly, this currently do not include switching from full sync to half sync and back during the starting (semi sequential during half sync and then switching to full sequential). So it needs to be updated in this regard.

Otherwise I too find the single enum more clear if this can be used, instead of multiple variable and bit.