ALFA diffractive triggers in HI L1/HLT menus [ATR-23602] in master

Adds the diffractive triggers needed for ALFA special runs. Tagging @ladamczy. The added triggers should correspond to the wishes in this comment.

In the process, I simplified the code in L1Seeds and tied the list of multiseeds using this code in DictFromChainName more strictly to the ones that are actually defined via a map to the concrete definitions. Keeping individual functions defined even for the very minimal lists is still useful for generality + readability. Unfortunately a few of the functions require more specific arguments, so I could not eliminate some hard-coding of lists, but now it is confined to 4 items and the hard-coding is in the same module as the logic.

Note that I have not yet enabled L1_DPHI-2eEM5_VTE5p24ETA49_ALFA_EINE, because this ended up as a mixture of legacy and Phase-I thresholds. We neither have a legacy TE5p24ETA49 threshold defined, nor what I think is the correct Phase-I threshold jTEFWD5 (numerical value might also need tuning). I'd propose to go ahead without this one trigger for now, but we should also write down what all the required jTE(C|FWD|FWDA|FWDC) thresholds are and define them. Tagging @astruebi and @lidiaz to bring this to their attention.