Merge commit '8dd99c8843ba968c8b98a1de0dd3377a94603a9e' as 'hub_test/src/tx_phase_ali...

Merge commit '8dd99c8843ba968c8b98a1de0dd3377a94603a9e' as 'hub_test/src/tx_phase_aligner'

Add TX phase aligner core from CERN HPTD project:

https://gitlab.cern.ch/HPTD/tx_phase_aligner

This achieves TX phase alignment to a reference clock by the method
described in:

E. Mendes, S. Baron, C. Soos, J. Troska and P. Novellini, "Achieving
Picosecond-Level Phase Stability in Timing Distribution Systems With
Xilinx Ultrascale Transceivers," in IEEE Transactions on Nuclear
Science, vol. 67, no. 3, pp. 473-481, March 2020, doi:
10.1109/TNS.2020.2968112.