bug(linux): Ibus tray icon does not use icon defined by layout on KDE Plasma

### Describe the bug

When using Keyman with ibus on KDE Plasma, the icon in the tray is the default keyman icon for all layouts, irrespective of the icon specified by the layout. The icon displayed in the Keyman Configuration application also seems broken, as it always displays as the default .kmp icon.

### Reproduce the bug

1. Install keyman on KDE Plasma with ibus.
2. Install any keyboard with a unique icon.
3. Observe that the tray icon is the default Keyman icon.

### Expected behavior

The tray icon should use the icon specified by the layout (if at all possible). Without this functionality the tray icon is functionally useless, as it only serves to tell the user they are using "a keyman layout".

### Related issues

_No response_

### Keyman apps

- [ ] Keyman for Android
- [ ] Keyman for iPhone and iPad
- [X] Keyman for Linux
- [ ] Keyman for macOS
- [ ] Keyman for Windows
- [ ] Keyman Developer
- [ ] KeymanWeb
- [ ] Other - give details at bottom of form

### Keyman version

16.0.144-1

### Operating system

Manjaro with KDE Plasma 5.27.11, Kernel 6.6.26-1

### Device

Custom desktop

### Target application

_No response_

### Browser

_No response_

### Keyboard name

_No response_

### Keyboard version

_No response_

### Language name

_No response_

### Additional context

_No response_