FEATURE: Add ability to only return specific index types

[slippman]

The present behavior

  -t, --type-filter TEXT          specify the index types to exclude.
                                  Supports multiple exclusions Eg: -t ISM -t
                                  SYSTEM

can be useful to exclude specific index types, but there should also be a (mostly mutally excuslive argument type) - that allows the user to only return a specific index type(s).

For example

optic index info -c mycluster --index_type ISM

would only return indexes that were of the type ISM. The command should allow for multiple types, i.e.

optic index info -c mycluster --index_type ISM --index_type SYSTEM

would return indexes of either ISM or SYSTEM type.