fix BSR report malformed, add SHORT BSR when it can (instead of LONG BSR)...

fix BSR report malformed, add SHORT BSR when it can (instead of LONG BSR) simplify the code and make the code more explicit, but the may structure remain (nr_write_ce_ulsch_pdu interface is complex, merging it into the called would make simpler and more interstandable code), fix some asserts related to this part of code

also, i can't test this MR alone with Nokia gNB, so maybe we will discover issues when we will pack a stack of MR and test again