Support resource creation in incremental annotation processors Allow resources to be created by incremental annotation processors using `Filer#createResource`. Allow resources to be created in the three currently existing output locations on `StandardLocation`: `SOURCE_OUTPUT`, `CLASS_OUTPUT`, and `NATIVE_HEADER_OUTPUT`.
A generated resource is uniquely identified by its `Location` and its path relative to that `Location`. A new type `GeneratedResource` is created to that effect. Data of that type is then plumbed through the existing annotation processing infrastructure, ultimately reaching `IncrementalCompilationInitializer` so that cleaning may be done.