Fix Text Overflow, OverlayBuilder's Builder Update, and Use Root Navigator Overlay

[AkramIzz]

The pull request introduces these changes:

• Fix text overflow: When text is longer than the screen width it overflows. The pull request fixes this by limiting the max width of the ToolTipWidget to screen width.

• Fix OverlayBuilder's didUpdateWidget: I noticed this issue when I changed the screen configuration of my device to landscape view, the overlay doesn't rebuild.

• Use root Navigator's Overlay: I had a page with a second navigator, and the showcase widget didn't work at all for me. Using the root navigator's overlay apparently fixed this. I believe this is due to how the overlay size and position are dependent on the screen size while the overlay (of the second navigator) is covering only part of the screen. I also couldn't think of a situation where someone would want to use an overlay other than the root Navigator's overlay for showcasing their app so I just used the root Navigator.

• Support for the ability to add padding to spotlight

[marianheinsen]

Thanks so much, this should definitely be merged. Using the root navigator's overlay fixed issues for me where tooltips were incorrectly positioned when using multiple nested navigators. @simform-solutions @BirjuVachhani @DevarshRanpara please review as this will help many others as well.

[vatsaltanna]

All these issues seem to be solved in the latest version of the showcase view, so we are closing this PR. We are glad to have your contribution to this repository. Thanks