Popover: Support full width button

[silvalaura]

I can't use a full width Button / Icon Button as the PopoverTrigger. Caldera needs this and we should support it.

Workaround:

const PopoverTriggerContainer = styled.div`
  & > div {
    width: 100% !important;
  }
`;

These custom styles allow us to force the trigger to be full width, but then we can't use target to set the container to also have that same width

Acceptance Criteria

1. A Button/IconButton inside the PopoverTrigger can use the isFullWidth prop from Button to receive full width styles
2. Using the width: target works as expected, or with any width