Add 2xl breakpoint to [hidden/visible]On[breakpoint] table cell visibility classes

[mcoker]

we have a new breakpoint $pf-global--breakpoint--2xl that should be supported with both visibleOn and hiddenOn with the classNames(Visibility.hidden, Visibility.visibleOnMd, Visibility.hiddenOnLg, ...) classes.

[tlabaj]

@priley86 for review of PR

[priley86]

sounds good... should be a simple add here hopefully:

https://github.com/patternfly/patternfly-react/blob/fdbde6d0fa3e6151300f1bbb8322a3308fb606c0/packages/patternfly-4/react-table/src/components/Table/utils/decorators/classNames.js

[kmcfaul]

Closed in #2676