[RNMobile] Prevent blocks being un-wantingly replaced with newly added blocks

[SiobhyB]

• Gutenberg Mobile: [RNMobile] Prevent blocks being un-wantingly replaced with newly added blocks wordpress-mobile/gutenberg-mobile#5569

What?

The changes in logic surrounding dictation handling in #49056 led to a regression where currently selected blocks are replaced with newly added blocks. This PR addresses that issue by reverting the changes to dictation introduced in #49056.

Why?

Fixes #49145

How?

• As part of [RNMobile] Fix dictation regression on iOS #49056, the isInsertingDictationResult bool was set to true for devices running iOS 16 or later. However, this meant that the textViewDidChange never ran, which then caused the focus/replacement regression:

gutenberg/packages/react-native-aztec/ios/RNTAztecView/RCTAztecView.swift

Lines 787 to 796 in d76d917

	func textViewDidChange(_ textView: UITextView) {
	guard isInsertingDictationResult == false else {
	return
	}
	propagateContentChanges()
	updatePlaceholderVisibility()
	//Necessary to send height information to JS after pasting text.
	textView.setNeedsLayout()
	}

• The removal of the logic that removed the objectPlaceholder also caused an obj symbol to display amidst text when previewed.

• With the above considered, the dictation fix has been reverted, so that the regression described in [RNMobile] Newly block replaces currently selected block on iOS #49145 is fixed and we can continue with the Gutenberg Mobile release.

Testing Instructions

It should be confirmed that these changes fix the regression it's addressing:

1. Navigate through the steps to create a new post in the iOS app.
2. Type some text into a paragraph block.
3. Tap the inserter in the editor's toolbar.
4. Select a new block to add to the editor.
5. Confirm that the new block is added beneath the currently select block, and that it doesn't replace it.

In addition, we should confirm that the changes in this PR don't cause further issues with dictation:

1. Navigate to My Site → Posts and create a new post.
2. Activate the iOS dictation feature and dictate some text.
3. Notice the text added to the editor.
4. Tap another block on the editor or begin typing onto the keyboard to confirm there is no content loss.
5. Experiment with adding various text and attempting to break dictation.

Screenshots or screencast

You'll see in the following screen recording that a newly added block is correctly added beneath a currently selected block (it doesn't replace the selected block):

replacement.mov

[github-actions]

Flaky tests detected in 2f6408f.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/4446524553
📝 Reported issues:

• [Flaky Test] doesn't throw a block error when clicking on a link #47747 in /test/e2e/specs/site-editor/template-part.spec.js

[fluiddot]

LGTM 🎊 ! Thanks @SiobhyB for fixing this 🏅 !

I tested it on a real device using iOS 15.4:

• Paragraph block with text is not replaced when adding a new block ✅
• Dictation works ✅

And on iOS 16 using a simulator:

• Paragraph block with text is not replaced when adding a new block ✅
• Dictation works ⚠️ : I noticed that after the dictation ends, the Unicode character \u{FFFC} is added but it's not removed (see attached video capture). I think the only side-effect of leaving the character is that adds extra empty space, so probably not a critical issue.

NOTE: The word I'm saying when dictating is hey.

Kapture.2023-03-17.at.10.58.28.mp4

[fluiddot]

I confirm the revert matches the original code. Thanks!