Add support for incremental annotation processors in KAPT. These
processors conform to https://docs.gradle.org/current/userguide/java_plugin.html#sec:incremental_annotation_processing
specification.
Support is provided by using javac compiler APIs and
recording the source file structure. At runtime, processors
are instrumented with custom Filer that is used to keep track of generated
files. In order to support classpath changes, stub generation task is
used to generated a list of changed FQCNs, and this is simply used by KAPT.
Both worker and non-worker mode are supported.
#KT-23880
1. Use 'KaptOptions' for all kapt options, including paths and flags.
2. Use a single 'KAPT_OPTIONS' compiler configuration key for setting all options (using a mutable KaptOptions.Builder).
3. Pass 'KaptOptions' instead of separate flags.
4. Remove 'KaptPaths'.
5. Remove deprecated 'aptOnly' CLI option.
Ivan Gavrilovic