HLT menu changes for letting multi jet chains being executed

Many changes, unfortunately all correlated:

• added ‘merged’ flag in the ChainProp to test the unsplitted chain names. This is needed because the chainDict in this way is created with the proper correct unsplitted chains, and L1Decoder accessing it can let these chains passing at L1
• added the array of ChainDict as critical member of the ChainStep: the len of this array must be equal to the number of sequences and the multiplicity (later the multiplicity can be removed to further simplify)
• having the ChainsDict of the legs, the ChainStep is able to set the Chain leg names in the Filter
• made the MinBias and Calib signatures using the menu functions for creating the ChainSteps in the correct way
• updated the emulation tests to use the new ChainSteps
• discovered a bug in the execution of Empty steps, that was preventing multi-jet chains to run properly (misconfiguration in the Empty legs connections to the Filter)

This is addressing ATR-22043