feat(developer): Support the "Snap-to-Grid" Approach to Touch Key Alignment

### Is your feature request related to a problem? Please describe.

In the Touch Layout view, it is often desirable to position a key so that it aligns with the key above or below. This can take some trial and error with setting the padding values, and then you may still be off by a pixel or two and not realize it. Feature Request #14593 is complementary to this one and also helps address the same issue.

### Describe the solution you'd like

When a key is dragged left or right within a row, KMD will "snap" it into alignment with keys in the row above and below. If the user accepts the "snap" positioning and releases the key, the "padding" value will be filled in accordingly. The user may manually reset the padding value at any time if desired.

The "Snap to Grid" positioning is a familiar approach used by many visual design tools. I can add some examples if needed.

### Describe alternatives you've considered

_No response_

### Related issues

_No response_

### Keyman apps

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

### Keyman version

18.0.238

### Operating system

Windows

### Device

N/A

### Target application

N/A

### Browser

N/A

### Keyboard name

N/A

### Keyboard version

N/A

### Language name

N/A

### Additional context

_No response_