bug(developer): generation of KVK from LDML keyboard seems to be creating an invalid .kvk file

[mcdurdin]

From: keymanapp/keyboards#2993
Continuing: #12278, #12284 (fixing #12056)

The imperial_aramaic.kvk file generated during the build has multiple issues:

1. It contains none of the keycap data; due to 17.0.328 compiler still referenced in keyboards repository.
2. The visualkeyboard.header.kbdname field is blank, but needs to be imperial_aramaic; see

   keyman/developer/src/kmc-ldml/src/compiler/visual-keyboard-compiler.ts

   Line 34 in 6353f92

   /* TODO-LDML: consider associatedKeyboard: this _must_ be set to id (aka basename sans ext) of keyboard .kmx file */

3. The shift and non-shift state data appears to be munged together (rather than separated into layer elements grouped by shift attribute); see

   keyman/developer/src/kmc-ldml/src/compiler/visual-keyboard-compiler.ts

   Line 100 in 6353f92

   // TODO-LDML: other modifiers

4. Some characters are encoded with \u{....} instead of being raw Unicode text, e.g. \u{0020}, and displays are missing; see

   keyman/developer/src/kmc-ldml/src/compiler/visual-keyboard-compiler.ts

   Line 88 in 6353f92

   text: keydef.output, // TODO-LDML: displays

[mcdurdin]

@srl295 @LornaSIL @DavidLRowe FYI. The visual keyboard compiler in kmc-ldml has multiple gaps, so will work on fixing those.