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• The PR title follows our guidelines: https://github.com/NativeScript/NativeScript/blob/master/tools/notes/CONTRIBUTING.md#commit-messages.
• There is an issue for the bug/feature this PR is for. To avoid wasting your time, it's best to open a suggestion issue first and wait for approval before working on it.
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• Tests for the changes are included - https://github.com/NativeScript/NativeScript/blob/master/tools/notes/WritingUnitTests.md.

What is the current behavior?

There are cases when iOS views display extra borders. That is because border layers/masks have no anti-aliasing.

What is the new behavior?

iOS view borders will draw properly using anti-aliasing on corresponding layers.
This is a replacement for PR #10600. Previous attempt was a hackish solution and it eventually caused new problems (thanks @rigor789 for letting me know)

Fixes/Closes #10548.