Consider using IBus semantic preedit hints

## Description
Under Wayland session, the current converting text segment is not highlighted. So users cannot understand which text segment they are converting.

## Steps to reproduce
Steps to reproduce the behavior:
1. Type 'watashinonamaeha'
2. Press Space

## Expected behavior

A converting text segment is highlighted.

## Actual behavior

No text highlight.

## Screenshots
See above

## Version or commit-id
Mozc-2.32.5981.102+24.11.oss

## Environment
- OS: openSUSE Leap 16.0
- IMF (for Linux): IBus
- Related Applications: Kate

## Investigations

## Additional context
A patch to fix this problem is ready for PR.