[llvm-mca] Add a new option category for views.
With this patch, options to add/tweak views are all grouped together in the
-help output.
The new "View Options" category looks like this:
```
View Options:
-dispatch-stats - Print dispatch statistics
-instruction-info - Print the instruction info view
-instruction-tables - Print instruction tables
-register-file-stats - Print register file statistics
-resource-pressure - Print the resource pressure view
-retire-stats - Print retire control unit statistics
-scheduler-stats - Print scheduler statistics
-timeline - Print the timeline view
-timeline-max-cycles=<uint> - Maximum number of cycles in the timeline view. Defaults to 80 cycles
-timeline-max-iterations=<uint> - Maximum number of iterations to print in timeline view
```
llvm-svn: 330816