Fix TextInput interfering with Japanese conversion

[christophpurrer]

Please select one of the following

• I am removing an existing difference between facebook/react-native and microsoft/react-native-macos 👍
• I am cherry-picking a change from Facebook's react-native into microsoft/react-native-macos 👍
• I am making a fix / change for the macOS implementation of react-native
• I am making a change required for Microsoft usage of react-native

Summary

The bug happened anywhere we set a onChangeText event handler on TextInput, and rewrite the inflight text such as shown in
https://github.com/microsoft/react-native-macos/blob/main/packages/rn-tester/js/examples/TextInput/TextInputSharedExamples.js#L137

To fix we have to ignore changes to text if we have incomplete conversions.

Changelog

[macOS] [Fixed] - Fix TextInput interfering with Japanese conversion

Test Plan

Go to macOS Preferences > Keyboard > Input Sources > add "Japanese Romaji". Use traditional conversion per https://support.apple.com/guide/japanese-input-method/enter-japanese-text-jpim10265/mac.

In the textInput type "watashi", select first auto complete option (e.g. press SPACE), then type "tachi", and confirm you get "私たち":

Before

私阿知

Screen.Recording.2022-08-11.at.3.54.41.PM.mov

After

私たち

after.mov

[Saadnajmi]

@chiuam didn't you fix something similar recently?
Edit: was thinking of #1296

[Saadnajmi]

Is this change verified for other languages other than Japanese? Will double check this doesn't conflict with #1296 before merging

[christophpurrer]

I would expect it happens to other languages as Japanese - which require a similar input style.
I can't verify that as I only know German, English, Spanish.
The issue was reported by Japanese speaking people internally, hence I only put that language into the title.
Thanks for double checking the change against #1296