Add MTI tag to counter metrics for transaction type identification

[op-transactility]

Each counter metric now includes the Message Type Identifier (MTI) as a tag, enabling better classification, grouping, and filtering of metrics by transaction type. This enhancement improves monitoring and observability by providing clearer insights into the volume and distribution of different transaction types (e.g., Authorizations vs Reversals).

Example of the updated metrics output:

# HELP jpos_isomsg_total Received messages
# TYPE jpos_isomsg_total counter
jpos_isomsg_total{direction="in",mti="2100",name="gateway",type="server"} 250000.0
jpos_isomsg_total{direction="in",mti="2400",name="gateway",type="server"} 150000.0
jpos_isomsg_total{direction="out",mti="2110",name="gateway",type="server"} 250000.0
jpos_isomsg_total{direction="out",mti="2410",name="gateway",type="server"} 150000.0