feat(toolbar): add vertical variant

[SimonFinney]

Affected issues

• Contributes to Toolbar 🏖️  #67
• Resolves Toolbar — orientation #806

Proposed changes

• Add toolbar vertical variant logic, stories, styles, and test
• Update default toolbar story to better reflect guidance
• Refactor common toolbar tests to better accommodate individual component tests

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[matthewgallo]

https://user-images.githubusercontent.com/10215203/130460308-af865b1d-ed6c-4840-96d0-a49abc9c2549.mov
For the vertical toolbar, it might be easier to use if the tooltip has the option to be placed from the left or right. You cannot easily hover over the item above the current toolbar item because the tooltip is on top of it.

[SimonFinney]

https://user-images.githubusercontent.com/10215203/130460308-af865b1d-ed6c-4840-96d0-a49abc9c2549.mov
For the vertical toolbar, it might be easier to use if the tooltip has the option to be placed from the left or right. You cannot easily hover over the item above the current toolbar item because the tooltip is on top of it.

@matthewgallo a quick update on this — the design recommendation is that the default tooltip position should be top for both orientations. I've created an issue and reduced test case in Carbon to investigate further, as it feels like a defect that may not affect just us.