Integrate irondash/cargokit for build

[sneurlax]

Replace build_all.sh with an irondash/cargokit integration.

[sneurlax]

This will probably be easiest to integrate through the generation of a fresh Flutter plugin repository.

[sneurlax]

This has been paused due to @julian-CStack's valid concerns over build times. Hopefully either irondash/cargokit or irondash/native_toolchain_rust can be used with a prebuilt binaries option to provide the best of both worlds: builds from source the first time, and use of cached libraries where possible.

[sneurlax]

cargokit can use prebuilt binaries