support showing a loading spinner and error tooltip on ActionItem during command execution
Created by: sqs
If the new ActionItem prop showLoadingSpinnerDuringExecution is true, then a loading spinner is shown after the button is pressed if it executes a command. This will be used by hover buttons.
Also adds support for showing the error inline on the button that executed the command. This is useful for errors that are scoped to a specific button instead of being global.
Used in #1313 but is useful by itself.
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