TriggerJobOpts+TriggerMenuMT: cleanup of legacy menu code/flags
Further cleanup of the legacy (Run-1&2) trigger menu code and flags.
Remove the following TriggerFlags and their uses:
readLVL1configFromXMLinputLVL1configFileoutputLVL1configFiletriggerMenuSetupmenuVersion
Note, that TriggerFlags.triggerConfig is kept for the moment as some further cleanup it 3rd-party jobOptions is needed first to make sure we are not breaking them unintentionally.
Also cleanup remaining legacy LVL1 menu code in TriggerMenuMT:
- remove usage of obsolete
TriggerFlags - delete remaining LVL1 legacy menu code
- delete unused
MenuUtil.py
Relates to ATR-21862.