Fix L1 config in MTCalibPeb test
Changes in TrigT1ResultByteStreamConfig
in !33608 (merged) made the configuration depend further on new-style flags and configuration. This broke the MTCalibPeb tests. Adapt the MTCalibPeb configuration to make it work again - fixes ATR-21678.
While adapting, allow also to specify the key two L1 flags (enableL1Phase1
and enableL1CaloLegacy
added in !33608 (merged)) from command line and ensure the test works well with and without the phase1 elements.