feat(Toolbar): add popup prop

[miroslavstastny]

Closes #1410.

A Toolbar item can now have a popup:

API

popup prop was added to the ToolbarItem. It is a shorthand for Popup component, accepting all config valid for Popup with the following exceptions:

• accessibility defaults to popupFocusTrapBehavior (but can be overriden)
• children prop cannot be used, it is always reset by the ToolbarItem
• trigger prop cannot be used, it is force-set to the ToolbarItem's button

Toolbar is a controlled component, it does not internally handle items' state. It is consumer's responsibility to handle MenuItem:active prop based on the Popup state.

[codecov]

Codecov Report

Merging #1480 into master will decrease coverage by 0.01%.
The diff coverage is 45.45%.

@@            Coverage Diff             @@
##           master    #1480      +/-   ##
==========================================
- Coverage   73.45%   73.44%   -0.02%     
==========================================
  Files         822      822              
  Lines        6183     6190       +7     
  Branches     1793     1795       +2     
==========================================
+ Hits         4542     4546       +4     
- Misses       1636     1639       +3     
  Partials        5        5

Impacted Files	Coverage Δ
packages/react/src/types.ts	50% <ø> (ø)	⬆️
packages/react/src/components/Popup/Popup.tsx	67.94% <100%> (+0.2%)	⬆️
packages/react-proptypes/src/index.ts	33.8% <16.66%> (-0.02%)	⬇️
...kages/react/src/components/Toolbar/ToolbarItem.tsx	85% <75%> (-3.24%)	⬇️

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[bmdalex]

looks good generally, couple of comments

[mnajdova]

Looks good 👍 ! Don't forget to add changelog entry.