Added support for comnbined chains in the Run2 to Run3 nav conversion

In the nav conversion we were not assigning all the right IDs to the navigation elements used in combined chains. This MR fixes that. It parses chain name to find the multiplicities and this seems not to work in all the cases. HLT_g3_loose_larpeb is decoded as having two legos of multiplicity: [1, 1] Tagging @burr on this (as he was the last person that changed chain name parsing). Anyways, it should not be harmful because there is only one TE at each step and the logic skips such TEs.

Another shortcoming, the Run 2 configuration is sometimes asymmetric with respect to the decoded multiplicity. For instance the: HLT_2g25_loose_g15_loose has decoded multiplicity [2, 1] but in this first step it has: [3] (i.e. 3 identical TEs required. Such cases TEs will not obtain extra leg chain ID.

Counting on experts: @tamartin to have a look.

@wprzygod - once this is merged it would be good to check if the combinations (reported by matching tools) are compatible for these chains.