feat: Have separate icons and titles for alpha and beta builds of Keyman

The alpha, beta, and stable releases are treated as separate products, which is why they can all be installed simultaneously. I think the appropriate solution here is to have a separate icon for the alpha + beta releases of Keyman, and probably change the App title to "Keyman Alpha" or "Keyman Beta".

_Originally posted by @mcdurdin in https://github.com/keymanapp/keyman/issues/7364#issuecomment-1260274697_

Raised originally for Keyman for Android but relevant for multiple platforms.