st_histogram updates. Ready for integration in LOFAR2.

Closes L2SDP-364

See merge request desp/hdl!137

-All test benches pass OK.

-All TB still pass OK (tb_tb_st_histogram).

-Added 5 TBs that use an unlocked, drifting sine wave as input.
-All test benches pass OK.

-Changed TB parameters.

Resolve L2SDP-431

Closes L2SDP-431

See merge request desp/hdl!136

simultaneous read/write issue;
-Added signed/unsigned histogram readout to TB;
-All test benches pass OK.

Use N_pol_bf = 2 for dual polarization BF, instead of using general N_pol = 2.

Closes L2SDP-469

See merge request desp/hdl!135

Resolve L2SDP-455

Closes L2SDP-455

See merge request desp/hdl!134

Also added:
- Parameterizable (partly automatic based on generics) sine wave generation;
- Option to lock sine wave to sync (sparse histogram) or not (dense histogram).

Still to do:
- Fix address readout bug in TB (causes shift in histogram in wave window)
- Add top level functional description
- Clean code

Also added:

    signed/unsigned histogram readout to st_histogram;
    Extra check in TB to check if verification was done at all;
    Added behavioural sine wave generation in TB;
    Added TB signals to display as Analog; allows viewing of input sine and resulting histogram.