chore(developer): make unknown vkey a hint, not error 🙀

Note that feat(core): ldml vkey support 🙀 #7135 is future,
in the future this may be an Error again.

- also, add an internal error to the visual-keyboard-compiler on missing keys
- also, update fr-t-k0-azerty to fix a missing key (simultaneous fix has been made in CLDR)
- also, reinstate CLDR's fr-t-k0-azerty - now all 'stock' keyboards build in keyman!
- keep the 'internal' azerty as k_020 - it has some additional transform goodies

Fixes: #9236