Update NR UE threading model
This updates the NR UE threading model by preventing calling threadpool
from threadpool and fixes deadlock issues related to processSlotTX. By
making processSlotTX run to completion instead of starting and waiting
for other threads to finish it prevents locking thread pool cores,
therefore prevening deadlocks.
There is a slight difference here compared to the previous version where
I do not use the UL actor as I believe it is not necessary,
processSlotTX satisfies the run-to-completion requirement now. If in the
future any UL procedure would be parallelized using the thread pool it
should either be done in a run-to-completion model or the processSlotTX
function should be taken off the thread pool.
The documentation has been updated.