Fix: Chat search doesn't work well in many cases with Japanese IMEs

[fumiakiy]

Contributor checklist

• I am following the Code Style Guidelines
• I have tested my contribution on these devices:

• Samsung Galaxy S22+ One UI 6.0 Android 14
• AVD Pixel 6a Android 14 Google Play

• My contribution is fully baked and ready to be merged as is
• I ensure that all the open issues my contribution fixes are mentioned in the commit message of my first commit using the Fixes #1234 syntax

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Description

In in-conversation search, you almost cannot use the search function in Japanese because the Gboard (and possibly other keyboards) keeps closing when you type a key. The very similar behavior is there for the emoji search in the chat input panel
as well. See the screen recordings below for details.

There are quite a few user reviews in Japanese in Google Play that submit the issue. I pasted the screenshots of some of the reviews.

Steps to reproduce the bug

1. Set up the device so your Gboard opens in Japanese mode (qwerty)
2. Open Signal, go to a chat (1:1 or group)
3. Menu > Search
4. Enter a consonant (b for example)

Observed:
Keyboard closes and the full-width "b" is committed in the edittext. Nothing will be found for the character (in most cases) in the search results.

Expected:
Keyboard stays open and the character is not committed, and the search doesn't start. Keep entering a valid word and search should work.

Screen recordings

Bug in chat search

pr-before.mp4

Bug in emoji search

pr-before-2.mp4

After the fix in this PR

pr-fixed.mp4

pr-fixed-2.mp4

[fumiakiy]

Here are some of the reviews in Google Play that point out the bug

[greyson-signal]

Thank you! We'll put this in 7.2 provided we don't experience any problems with it (this is definitely a finnicky area of the codebase!)