Width 100% on dropdown has container expanding too much

[ArakTaiRoth]

Info

If you use any percentage width (not just width="100%") with the Dropdown right now, it causes the actual open state of the Dropdown to expand far past the viewport in width.

This is happening because the Dropdown passes the same width it's assigned to the Popover (so 100% for example). That width is then applied to the Popover container, where the percentage is not guaranteed to resolve against the same parent container as the Dropdown.

More Info

It was reported by Vidit that this issue also exists for Datepicker

Acceptance Criteria:

1. When using percentage width on Dropdown, the open width should match the closed width
2. When using percentage width on Datepicker, the open width should still not exceed the maximum width