Merge remote-tracking branch 'origin/nrLDPC_coding_improvements_3' into integration_2025_w08 (!3227)

fix(nrLDPC_coding): timers in DL encoding, fix(ldpctest): Confusion in sizes

Main improvements:

1. fix(ldpctest): Confusion in sizes
   IMPORTANT: This fix makes that ldpctest now works with BG2 and K' != K!
   (Worth double checking with more cases than I did check with though)
   The variable block_length had an ambiguous role and was used as both K and
   Kprime. This was leading to arrays with wrong sizes and functions with wrong
   arguments. Now there is not anymore block_length but K and Kprime.
   Kprime can be set with the command line argument -l.
   There was also some problems with array allocation for segments with length
   not divisible by 8. A proper sizing with ((size_in_bits + 7) & ~7) / 8 was
   used.
   A proper masking of the last byte containing payload bits was also added to
   keep filler bits to 0 after random initialization.

2. fix(nrLDPC_coding): timers in DL encoding
   While timers were available for rate matching and interleaving in the new
   interface, these timers were not merged to rate matching and interleaving
   timers in nr_dlsch_coding.