[core] fix(Drawer): allow clicking on overlaid contents when hasBackdrop=false

[joncelay]

Fixes #3515

Checklist

• Includes tests (n/a)
• Update documentation (n/a)

Changes proposed in this pull request:

Remove the modal trait of Drawer when hasBackdrop is set to false
by making overlay container styles conditional to hasBackdrop.

Reviewers should focus on:

• Verify the behavior with and without portal
• Verify the scrolling of Drawer content on smaller screen size
• Note that canOutsideClickClose becomes ignore when hasBackdrop is false

Screenshot

New: clicking outside the drawer discards it and changes the position selection

Old: clicking outside the drawer discards it. An additional click is required to change the position selection

[joncelay]

Removing the margin to prevent the button from jumping:

[adidahiya]

extract className from props

Build artifact links for this commit: documentation | landing | table | demo

This is an automated comment from the deploy-preview CircleCI job.

[adidahiya]

This seems to work well and it is a good improvement over the default. It is a behavior change compared to the current <Drawer hasBackdrop={false}> (which can sometimes be considered breaking), but I think it will be a welcome one. Users are already able to scroll the contents behind a drawer when hasBackdrop={false}:

this just makes it so that they can also click on the content underneath, as you demonstrated above 👍

[adidahiya]

I realize now that this "overlay container" class (added in #2957) has a somewhat misleading name since it's only used by the Drawer component and it's non-descriptive about its purpose... it might make more sense to call this "OVERLAY_FIXED_BACKDROP" or something like that. We can't change it now though; it's part of the public API... just musing about the name here, perhaps I'll add some code comments about this in a separate PR.