The previous values of the BSR timers would "starve" the UE: to my
understanding, constant UL traffic would not make any BSR timer expire,
and thus, no new BSRs were sent by the UE. However, since they were too
infrequent, the gNB thought there was no data anymore after serving the
UE for some slots.  Hence, reduce the timers to have constant UE buffer
feedback. Maybe they have to be increased if we ever have many UEs...

The TDA change used a binary search (worst case O(log n)) for finding
the right amount of RBs, whereas everywhere else we used a linear search
(O(n)). We generalize the binary search into a function nr_find_nb_rb()
and use it for DL and UL allocation.

Note: Need to maintain same PDSCH and PUSCH TDA list lengths

If the PDSCH and PUSCH TDA lists have different lengths (before this
commit, PDSCH TDA list length was 2, for PUSCH 3), the OAI UE would get
confused: In the special case, the TDA in the DCI for UL was incorrectly
calculated, and a change of the PDSCH TDA list triggered UL never being
decoded correctly.