Create hybrid configuration example

[stepango]

Introduce stub targets

feature-api
feature-impl
feature-stub

introduce new API for adding project dependencies
During IDE sync impl will be substituted with stub for improved IDE performance, using (compileOnly+runtimeOnly/implementation) configuration based on local flags

[stepango]

Done on v2 via hybrid configuration:

• F-103 example: examples/android/15-hybrid-targets (api/impl/stub-impl co-location)
• F-104 engine + flag: docs/HYBRID-CONFIGURATION.md, featureImplementation / target flag gating, useFeatureStubs / -Pforma.useFeatureStubs

Closing as completed. Simple swap v1 (not dual compileOnly+impl default).