[ios] fix overlapping drawing surface with the "safe area"

[kambala-decapitator]

Description

UI no longer appears under the "notch" of new iPhones (X and later). Screenshots were taken from iPhone XR and framed with fastlane.

Motivation and Context

Currently UI is partially cut by the notch, sometimes it cuts essential parts of the UI. See screenshots for examples.

How Has This Been Tested?

• iPhone XR: to test new behavior
• iPhone 6+, iPhone 6s, iPhone 5, iPad Air 2: to verify that old behaviour still works the same way

Screenshots (old vs new):

1 left

1 right

2 left

2 right

3 left

3 right

4 left

4 right

Types of change

• Bug fix (non-breaking change which fixes an issue)
• Clean up (non-breaking change which removes non-working, unmaintained functionality)
• Improvement (non-breaking change which improves existing functionality)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that will cause existing functionality to change)
• Cosmetic change (non-breaking change that doesn't touch code)
• None of the above (please explain below)

Checklist:

• My code follows the Code Guidelines of this project
• My change requires a change to the documentation, either Doxygen or wiki
• I have updated the documentation accordingly
• I have read the Contributing document
• I have added tests to cover my change
• All new and existing tests passed