Allow to configure new dropdowns' panel to stretch full-size on certain screen sizes or based on `block` prop

The following discussion from !3233 (merged) should be addressed:

• @matejlatin started a discussion: (+2 comments)

  @ohoral when you start working on this, can you please also make the dropdowns 100% width on small screen devices. Here's a recent relevant discussion about it.

We should either make a default behavior as suggested in the comment above or allow to configure via panelClass or some component property - this is to be discussed.