Updates the tooling to use the GTK embedding, rather than the GLFW embedding:
- Adds new requirements to `doctor`
- Updates the app and plugin templates to make GTK-based runners and plugins
- Stops downloading and installing the GLFW artifacts
Final part of #54860, other than cleanup.
Updates the Linux templates to use CMake+ninja, rather than Make, and updates the tooling to generate CMake support files rather than Make support files, and to drive the build using cmake and ninja.
Also updates doctor to check for cmake and ninja in place of make.
Note: While we could use CMake+Make rather than CMake+ninja, in testing ninja handled the tool_backend.sh call much better, calling it only once rather than once per dependent target. While it does add another dependency that people are less likely to already have, it's widely available in package managers, as well as being available as a direct download. Longer term, we could potentially switch from ninja to Make if it's an issue.
Fixes#52751
