[Enhancement] Make `usePopover` default behavior in dropdown

[x] I have written a good issue

Describe the enhancement

There are some reports about dropdown not correctly placing itself on top of content , e.g. #3691 and others raised in our support channels. These have proven to be solved by usePopover="true", so we should make it the default. It is battle-tested, and known issues have been solved as per https://github.com/kirbydesign/designsystem/issues/2087.

Solving this issue will also solve above mentioned issue (#2087).

Also, consumers have to explicitly set usePopover for dropdown in calendar, which is not ideal, and would also be solved by this.

Describe the solution you'd like

Make usePopover true by default and deprecate the input all together, by warning when it is set. Remove the input all together in the next major.

Are there any additional context?

Checklist:

The following tasks should be carried out in sequence in order to follow the process of contributing correctly.

Refinement

[ ] Request that the issue is UX refined
[ ] Request that the issue is tech refined; do not proceed until this is done.

Implementation

The contributor who wants to implement this issue should:

[ ] Make sure you have read: "Before you get coding".
[ ] Signal to others you are working on the issue by assigning yourself.
[ ] Create a branch from the develop branch following our branch naming convention.
[ ] Publish a WIP implementation to Github as a draft PR and ask for feedback.
[ ] Make sure you have implemented tests following the guidelines in: "The good: Test".
[ ] Update the cookbook with examples and showcases.

Review

Once the issue has been implemented and is ready for review:

[ ] Do a self-review.
[ ] Create a pull-request. If you created a draft PR during implementation you can just mark that as "ready for review".

kirbydesign / designsystem