Toolbar - refactor to allow for attribute-value search

[nicolethoen]

Currently, a Toolbar is wired so that each ToolbarFilter can have only one category of applied filters (chip groups) corresponding to it. This relationship is not flexible enough to allow for a single control (i.e. an attribute-value search) to generate multiple chip groups.

It's possible this is not feasible to simply refactor the toolbar to accommodate this request without introducing breaking changes. But it may be possible to expose the various pieces of a toolbar to allow this variant to be built composably.

This is a snapshot of the desired outcome:

[mcarrano]

Potentially large effort. May need core updates.

[nicolethoen]

Will be addressed in : patternfly/pf-roadmap#13