Duo SDK memory leak and Performance fixes

[PureWeen]

Description of Change

• added a sample with nesting a TPV into a CV to really push the TPV and make sure it doesn't deadlock and resources clean up
• updated the dualscreen gallery to latest androidx bits
• Fixed spanning bounds to compare the rectangles so it doesn't fire too many property changed events
• Wired up weakeventmanagers, weakreferences, and conditionalweaktables everywhere on android so that dual layout monitoring doesn't cause renderers to stick around in memory
• Fixed duo services to still report back landscape changes correctly even when not on duo devices
• Changed all properties that use the ScreenHelper to just set once opposed to reaching over the bridge with every request
• Moved all the enums out to their own files

Platforms Affected

• Core/XAML (all platforms)
• iOS
• Android
• UWP

Testing Procedure

• Run the DualScreen.SLN and you can test out the TwoPaneView from there. You might have to compile some of the platform projects individually because of multitargeting

PR Checklist

• Targets the correct branch
• Tests are passing (or failures are unrelated)