B2OC: Tune BdToD0hh_D0ToHH(HH) lines

FYI @mwhitehe @tlatham

We expect the changes to result in roughly the following rates and efficiencies

Line                     Rate (Hz)    Rate Reduction Factor    Efficiency (%)    Efficiency Reduction Factor
-------------------  -----------  -----------------------  ----------------  -----------------------------
BdToD0KPi_D0ToHH              80                0.102564           2.26963                        0.766544
BdToD0PiPi_D0ToHH             20                0.0909091          6.67828                        0.859244
BdToD0KK_D0ToHH               60                0.1875             0.15784                        0.659091
BdToD0KPi_D0ToHHHH           190               0.506667            4.17                           0.854508
BdToD0PiPi_D0ToHHHH           75               0.0986842           0.34                           0.586207
BdToD0KK_D0ToHHHH             55               0.141026            0.75                           0.765306

Where the reduction factors are calculated as the fraction of events that pass both the line with our cuts applied and the line as it was when @abertoli and @shunan applied their "machete" cuts.

We've added a new B builder for b_to_cstarhh since D* lines previously used the b_to_dhh builder which now features a default D flight-distance cut which is useless for D* (when done just on the B child) so the D* builder defaults to an extremely loose minimum FD.

Note: Efficiency was calculated with BdToD0PiPi_D0ToKPi MC for the D0ToHH lines and BdToD0KPi_D0ToKPiPiPi MC for the D0ToHHHH lines.