Implementing prescaling for trigger validation in TMMT

Addressing ATR-21613.

Adding writing/using of prescale sets (@mark ):

• !34964 (e4113401) - L1Menu has to accept that the menuName now will contain the prescale from the new menu name LS2_v1_TriggerValidation_mc_prescale, also added to the menu mapping to know which menu to build.

• !34964 (36e90a6f) - Add prescales to chains in GenerateMenuMT.py (1 by default) and then update using applyHLTPrescale in MenuUtil.py

• !34964 (ec2017ab) - move the default HLTPrescale JSON creation createHLTPrescalesFileFromMenu from TrigConfigSvcCfg.py to HLTPrescaleJSON.py in TriggerMenuMT. Also some code commented that probably can just be removed

• !34964 (c57d03e0) - now actually set chain prescale and enabled flag based on chain dictionary

• mark/athena@60642111 - fixes issue for finding L1xml file name

Setting which triggers to disable (@tvazquez )

• Disabled triggers starts by using a list disable_chain_list with triggers explicitly defined, work in progress moving to use a group in the menu.

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Status chains now disabled in the menu LS2_v1_TriggerValidation_mc_prescale will be disabled when running. The relevant tests that are affected in ATR-21613 will need the menu changing to this rather than LS2_v1.

Future work will be adding stream prescale information ATR-21324 and currently remaking whole menus where only the name changes so to avoid duplicates should neaten this procedure to use the same names (will follow up on ATR-20878)