Add support for annotations in the Java networknt implementation harness

[VIDIT45AGARWAL]

As per the discussion on slack, added annotation support for networknt implementation without breaking the existing bowtie commands.
Now when the run command includes "collect_annotations": true, the harness switches from simple validation to annotation collection, while without the flag behavior is identical to the current upstream harness.

Working

• A new collectAnnotations() method recursively walks the OutputUnit tree returned by networknt and extracts annotations as a nested map: instanceLocation → keyword → schemaLocation → value
• The TestResult record now has an optional annotations field, annotated with @JsonInclude(NON_EMPTY) so it is completely omitted from the JSON output when not in annotation mode
• The Test record's valid field was changed from boolean to JsonNode to handle annotation test cases that may not have a valid field

Testing

# Build
docker build -t networknt-test implementations/java-networknt-json-schema-validator/

# Validation mode (no flag — should show only valid field)
printf '{"cmd":"start","version":1}\n{"cmd":"dialect","dialect":"https://json-schema.org/draft/2020-12/schema"}\n{"cmd":"run","seq":1,"case":{"description":"type check","schema":{"type":"string"},"tests":[{"description":"valid","instance":"hello"},{"description":"invalid","instance":42}]}}\n{"cmd":"stop"}\n' | docker run --rm -i networknt-test

# Annotation mode (with flag — should show annotations)
printf '{"cmd":"start","version":1}\n{"cmd":"dialect","dialect":"https://json-schema.org/draft/2020-12/schema"}\n{"cmd":"run","seq":1,"collect_annotations":true,"case":{"description":"title test","schema":{"title":"My Schema","type":"string"},"tests":[{"description":"a string","instance":"hello"}]}}\n{"cmd":"stop"}\n' | docker run --rm -i networknt-test

Output

# Validation mode
{"ok":true}
{"seq":1,"results":[{"valid":true},{"valid":false}]}

# Annotation mode
{"ok":true}
{"seq":1,"results":[{"valid":true,"annotations":{"":{"title":{"#":"My Schema"}}}}]}

[Julian]

We'll come back to this (harnesses) once something like #2642 is merged