fix(text-view): only reload text if hint is showing on ios

[dosomder]

PR Checklist

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• 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/WritingUnitTests.md.

What is the current behavior?

iOS TextView reloads text every time the TextView is focused

What is the new behavior?

Only reload text if necessary (i.e. previously was the hint shown)

Fixes/Implements/Closes #8620

[dosomder]

@NathanWalker rebased on master to fix merge conflicts

[NathanWalker]

Thanks @dosomder

[dosomder]

@NathanWalker Do you know when this is planned to be merged / released?

[NathanWalker]

This will go out this week in a patch update 👍

[dosomder]

Looking forward to the release 👍

[NathanWalker]

Released with https://github.com/NativeScript/NativeScript/releases/tag/6.5.9 now