[iOS][BottomSheetController] Fix issues with corner radius and shadow when glass is enabled

[nodes11]

Platforms Impacted

• iOS
• visionOS
• macOS

Description of changes

A couple of issues have come up since the previous change which improved iOS 26+ glass support for the BottomSheetController.

1. The corner radius is not visible - The effectView was a missing a call to set its layer's masksToBounds property to true. Adding this call fixes the issue.
2. The shadow is missing from the edge of the sheet - Initially it appeared that the shadow applied to the bottom sheet did not work well with glass support. However, after more investigation and an ask to add it back, it was discovered that we were having issues because the shadow was being applied to the wrong layer. To fix the issue, we need to apply the shadow on the bottom sheet's parent view layer.

Binary change

n/a

Verification

• Validated in demo controllers
• Validated in internal use cases

Visual Verification

Pull request checklist

This PR has considered:

• Light and Dark appearances
• iOS supported versions (all major versions greater than or equal current target deployment version)
• VoiceOver and Keyboard Accessibility
• Internationalization and Right to Left layouts
• Different resolutions (1x, 2x, 3x)
• Size classes and window sizes (iPhone vs iPad, notched devices, multitasking, different window sizes, etc)
• iPad Pointer interaction
• SwiftUI consumption (validation or new demo scenarios needed)
• Objective-C exposure (provide it only if needed)

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