Names can be Unicode strings or byte arrays. This change allows for both
kinds. Also properly deal with the case when we can't get the name from
the .ttf file. And finally change the test so that we don't need the
`KbdKhmr.ttf` font.
This change adds the `keymanFacename` attribute based on UnicodeFont
or AnsiFont to the root element of the generated .ldml file so that
onboard-keyman can display the proper font for the osk.
Fixes: #12019