Introducing file system watching

Gradle 6.5 introduced an experimental file system watching feature, which became production-ready in Gradle 6.7. Instead of discarding file system state between builds, the Gradle daemon uses OS-level file system notifications to maintain a virtual file system across builds, avoiding redundant disk I/O. This results in faster incremental builds — benchmarks on the Santa Tracker Android project showed ~150ms (20%) improvement. The feature can be enabled via the `--watch-fs` flag or by setting `org.gradle.vfs.watch=true` in `gradle.properties`.