EMTF muon shower unpacker update (backport of PR41993)

[epalencia]

This PR fixes a bunch of things in muon shower unpacking in EMTF. It's not critical for data taking, but it will be good to backport it so we can improve monitoring of this trigger for 2023.

The changes are as follows:

• Changed the internal name of the trigger from HMT to "muon shower" or "MUS". This is done for consistency with other L1T trigger producers
• Added a proper way of creating CSCShowerDigi in EMTF unpacker. This was mostly done to adjust the BX value associated with the shower (but also follows the same pattern with other EMTF inputs)
• Added support for new loose shower bit in unpacked EMTF outputs
• Removed pure muon shower objects from EMTF hit and track collections. This should fix the unnecessary LogWarning messages originating from EMTF unpacker or emulator

There will be a PR to include the BX value in EMTF emulator (and potentially uGMT as well) in the future, but for now I wanted to keep these separate.

Backport of cms-sw#41993.

[epalencia]

Tagged as l1t-integration-v161.