Merge remote-tracking branch 'origin/ldpc_encoder_ZC384_optimization' into integration_2025_w36 (!3614)

Ldpc encoder zc384 optimization

This is a modification for the ldpc encoder which improves performance for
high-throughput cases. It contains a newly-generated file for innermost part of
the parity bit generation which, for AVX512, uses the mm512_permutex2var_epi8
instruction and for 128-bit (aarch64) the mm_alignr_epi8 (vextq_s8) in the
computation corresponding to each non-zero bit of the H matrix. This allows for
removing a very large memcpy and reduces the memory demand for the parity matrix
computation. For the moment this is limited to largest case in BG1, namely
Zc=384. This is the only format used when the number of segments after codeblock
segmentation is large (>8). This improves the timing required for ldpc parity
bits generation by more than a factor 2 with AVX512. This significantly reduces
the total time to generate the DLSCH/PDSCH.

See the merge request description for numbers.

openair1/SIMULATION/NR_PHY/dlsim.c

@@ -1032,6 +1032,7 @@ printf("%d\n", slot);
     reset_meas(&gNB->dlsch_rate_matching_stats);
     reset_meas(&gNB->dlsch_segmentation_stats);
     reset_meas(&gNB->dlsch_modulation_stats);
+    reset_meas(&gNB->dlsch_precoding_stats);
     reset_meas(&gNB->dlsch_encoding_stats);
     reset_meas(&gNB->dci_generation_stats);
     reset_meas(&gNB->tinput);