refactor(developer): move filename consistency check to kmc

kmcmplib no longer has any filesystem access, so it cannot verify if a
referenced filename in a source file has the same case as the actual
filename on disk (a risk when moving projects between platforms). So
I opted to move this to the `loadFile` callback in kmc, which is the
only place where filesystem is actually accessed, and added
corresponding unit test.

Small additional fixes here:

1. Move from `Buffer` to `Uint8Array` in all kmc-* modules, so that we
   remove that barrier to running on web.
2. Use `callbacks.loadFile` instead of `callbacks.fs.readFileSync`, so
   that we can be sure to run the filename consistency check.
3. Fixed kps parser silently swallowing xml errors on load.
4. Added silent mode to NodeCompilerCallbacks so we could cleanly test
   the new filename consistency hint.
5. Noted a location where we still have NodeJS deps in kmc-ldml.