Modify RD line B2XMuMu to form candidates using charged hyperons

Merge request that adds Ξ⁻ → Λ⁰ π⁻ and Ω⁻ → Λ⁰ K⁻ as possible B children to the Rare Decays stripping line B2XMuMu.

Paging @kreps to take a look as one of the line responsibles.

I ran the TestMyStrippingLine.py script over 50000 events with my modified version of the line:

StrippingReport                                                INFO Event 50000, Good event 44100
 |                                              *Decision name*|*Rate,%*|*Accepted*| *Mult*|*ms/evt*|
 |_StrippingGlobal_                                            |  0.3946|       174|       |  13.854|
 |_StrippingSequenceStreamLeptonic_                            |  0.3946|       174|       |  13.846|
 |!StrippingB2XMuMu_Line                                       |  0.3946|       174|  6.270|  12.061|
 |!StrippingB2XMuMu_Line_TIMING                                |  0.3855|       170|  6.418|   0.089|

So the retention and timing are both fine for an MDST line. In these 50000 events 3 B candidates are formed using hyperons, and 174 events are saved in total, so the change in retention is small.

One mildly concerning thing, I think unrelated to my changes, is that TestMyStrippingLine manages to select a different number of candidates in the _TIMING version.

It seems to be connected to errors like these:

B2XMuMu_a1k1_SubPIDAlg                                      WARNING SubstitutePID:: Maximum number of allowed particles reached
B2XMuMu_a1k1_SubPIDAlgp                                     WARNING SubPIDMMFilter:: Maximum number of allowed particles reached

The number of times this error appears tallies with the discrepancy in number of events selected (four). A naive guess is that the same SubstitutePID tool is used in the _TIMING version of the line and that the particle limit is per-event, but this is only a guess.