* Enables identification of KMXPlus files in processor factory
* Adds a stub action to generate an 'a' output character
* Adds a passing null_keyboard unit test for a hypothetical ldml
  keyboard

Establishes baseline class and headers, and stub for loading LDML
keyboards embedded in kmxplus files.

Part of #7045.

Indicates that the .kmx file has additional header structure immediately
following the COMP_KEYBOARD header. Used by KMXPlus file format for
supporting LDML keyboards. Requires VERSION_160 or higher in keyboard
file.

Fixes #7044.

Groundwork for KMXPlus file format for LDML keyboard support.

auto: increment master version to 16.0.44

change(web): updates mobile screen dimension detection code ⬅️

change(web): rotation polish - OSK reload no longer needed ⬅️

chore(common): build-utils.sh minor tweaks

chore(core): get wasm core building again

refactor(web): converts test_utils funcs to Promise use 🤝

chore(web): centralizes web-based modules' CI unit test configurations 🤝

auto: increment master version to 16.0.43

Updates search for emscripten if not on path, and fixes up unit test
infrastructure for wasm builds for new tests.

chore(common): GitHub issue template tweaks

fix(developer): rebuilding a model would not refresh it in server 🎾

fix(developer): increase maximum file size for server 🎾

Just incorporates some additional fields and instructions that I have
noted over time.

@keymanapp-test-bot skip

feat(developer): add languageUsesCasing to Model Editor