[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