bug(windows): on screen keyboard does not match mnemonic layout

Mnemonic layouts on Windows work well for typing, but the OSK (visual keyboard) does not match the keystrokes. This is because the mnemonic layout recompiler does not also rewrite the .kvk when it rewrites the .kmx.

Not sure if this should be classified as a bug or new feature -- but it's not great as it is.

Something we need to revisit.

Ref: https://community.software.sil.org/t/galaxy-greek-mnemonic-on-screen-kb/7621