feat(developer): Add option to clear data when shutting down Keyman Developer Server

### Describe the bug

In previous versions of Keyman before the rebuild when I had to use Browser tools to emulate Android, I believe the web debugger only ever showed the keyboard you were actively debugging while Keyman was open (unless you had multiple packaged together).

Since I started testing in 16 (currently 16.0.109), the debug window keeps filling up with old keyboards I have debugged on previous days, even after a restart.

In this screenshot, after a fresh restart, you can see that I'm only debugging `french_model`, but you also see both of my Cameroon keyboards.

Since I have multiple keyboards, I have to select the keyboard every time I load the browser, which is a small annoyance. Is this a cache-clearing bug that I've found or a new feature??

Also, where is the web server cache stored if I did want to inspect it?

_Note: I post on the community when I think the solution might reasonably help others, and here when it's a directed conversation with you folks._

### Reproduce the bug

1. Compile a touch keyboard and test it in your browser.
2. Restart the computer.
3. Open Keyman Dev and a new keyboard.
4. Compile and test in the browser.
5. Notice that both keyboards are available from the dropdown.

### Expected behavior

I would expect the caches to be cleared when the debugger closes.

### 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
- [X] KeymanWeb
- [ ] Other - give details at bottom of form

### Keyman version

16.0.109

### Operating system

Win 11 22H2

### Device

Lenovo c930

### Target application

Chrome or Edge

### Browser

Chrome or Edge

### Keyboard name

french_model, Cameroon Qwerty, etc.

### Keyboard version

_No response_

### Language name

_No response_

### Additional context

_No response_