[ENHANCEMENT]: Use popover

[alxzak]

Where are we now?

With #1671 the input property usePopover was introduced to the dropdown. When this is enabled the PopoverComponent is used to position the pop-out box.

This was done in order to be able to solve the bugs mentioned in the description of the aforementioned PR.

usePopover is set to false by default as we're not certain if it will introduce any bugs. Per 14. March 2022, testing has begun where some consumers of Kirby try to set usePopover="true" for their dropdowns.

What's next?

The goal is to eventually have usePopover="true" be the default. To do this we must:

1. Solve any reported bugs from consumer projects testing the popover functionality (if any).
2. Decide in which major version we will make it default. As soon as we know, we should implement a deprecation warning, letting people know that the default value will be change.
3. In the decided major remove the usePopover input property and just use the functionality per default.

Issues popover will allow us to solve:

• [BLOCKED][BUG] Dropdown doesn't popout correctly when the height of the popped out card reaches the viewport of its container #1411
• [BLOCKED][Enhancement] Responsive Actionsheet (On large screens) #404
• [Enhancement] Support horizontally centered dropdown #1772 (comment)
• [BUG] Dropdown Switching Sides on Small Screens #1683

Related issues:

• [BUG] Dropdown with popover has flashing blue outline #1792
• [Enhancement] Find a better way to lock scroll for Popover #1793 (same solution used for this should probably also be used to solve: [BUG] hiding scrollbar makes content shift when using FAB and Actionsheet a.o. #1543)

Other:

• Ionic 6 (upgrade issue here: [Housekeeping] Upgrade to Ionic 6 #1932) introduces a ion-popover component. We could experiment with replacing our own PopoverComponent with their implementation.