[llvm-mca][scheduler-stats] Print issued micro opcodes per cycle. NFCI

[llvm-mca][scheduler-stats] Print issued micro opcodes per cycle. NFCI

It makes more sense to print out the number of micro opcodes that are issued
every cycle rather than the number of instructions issued per cycle.
This behavior is also consistent with the dispatch-stats: numbers from the two
views can now be easily compared.

llvm-svn: 357919