feat: add error status to dropdown button

[TCL735]

Supports influxdata/ui#3404 - a new set of dropdowns will be put into Band View's options to allow the user to select only valid column names. The 3 different columns that have selectable names must choose different names. Indicate to the user that a dropdown has an invalid selection.

This is a minimalist feature. It simply allows the Dropdown.Button to add a box-shadow when the component status is error. Completely opt-in and backwards compatible.

Changes

• adds component status to Dropdown buttons
• adds box shadow to indicate error status for Dropdown buttons

Screenshots

UPDATED to use a solid border without shadow:

Checklist

Check all that apply

• Updated documentation to reflect changes
• Added entry to top of Changelog with link to PR (not issue)
• Tests pass
• Peer reviewed and approved
• Signed CLA (if not already signed)

[TCL735]

Regarding adding an error message for more visibility: yes, this is possible and is done by the consumer of Clockface. Within the <Dropdown> component, a developer may add additional elements adjacent to the <Dropdown.Button> as an error message. This is not done by default in Clockface because Clockface should not have an opinion on whether an error message is necessary or not.

[mavarius]

Let's make it have a solid border like the input components instead of the glow. It might also be good to get the red alert icon in there but that's not required for the issue fix.

[TCL735]

Updated to use solid border without shadow.