wb_intercon: Rename sdt to rdt in wb_arbiter
wb_intercon: Rewrite wb_mux to avoid placing select logic outside of module

wb_mux previously used a slave_sel_i input and required that the slave
select logic was placed outside the module.
This is changed so that the parameters MATCH_ADDR and MATCH_MASK are used
to select slaves instead. Updates to the test bench are in this commit too