Separate task classes to support incremental builds #4
Description
Tasks are currently implement with lambdas. See for example https://github.com/modelix/mpsbuild/blob/878a20dadbb3cdc0f0f1e86776c8fe201cb2b7b7/gradle-mpsbuild-plugin/src/main/kotlin/org/modelix/gradle/mpsbuild/MPSBuildPlugin.kt#L110
Incremental build don't work with them. The tasks are re-executed even if the input didn't change. To support incremental builds we have to move the implementation to a separate class with well defined inputs/outputs.
See https://github.com/modelix/modelix.core/blob/main/metamodel-gradle/src/main/kotlin/org/modelix/metamodel/gradle/GenerateMetaModelSources.kt for an example how it's done correctly.