Analyzer::Java

Shared helpers for the Java analyzers. They each extend Analyzer directly rather than a language-specific engine (historically the Java set was the first family to land and never got an intermediate class), so the helpers live as class methods on the JavaEngine module and the callers import it explicitly. Mirrors the pattern Analyzer::Kotlin::KotlinEngine follows. Helpers that need the analyzer instance (read_file_content) are private instance methods instead, picked up with include JavaEngine — the JAX-RS family and the Spring/Micronaut config readers, Kotlin Spring included.