[Improvement] Complete v2 audit operation mapping coverage

[FANNG1]

What changed

• Added explicit v2 audit mappings for all known OperationType values in CompatibilityUtils
• Expanded AuditLog.Operation with the concrete audit operation values needed by v2
• Added tests to verify:
  • concrete mappings for newly covered operation types
  • all known OperationType values map to a non-unknown audit operation

Why

The previous v2 compatibility mapping only covered part of the listener operation space.
Many supported operations still fell back to UNKNOWN_OPERATION, which made audit output incomplete and inconsistent.

This change makes v2 audit mapping complete for all known operation types and keeps UNKNOWN_OPERATION reserved for truly unknown inputs only.

How it was tested

IT_SPARK_HOME=/Users/fanng/deploy/demo/spark-3.5.3-bin-hadoop3 
IT_SPARK_ARGS='--conf spark.jars=/Users/fanng/deploy/demo/jars/iceberg-spark-runtime-3.5_2.12-1.9.2.jar,/Users/fanng/deploy/demo/jars/iceberg-aws-bundle-1.9.2.jar --conf spark.sql.extensions=org.apache.iceberg.spark.extensions.IcebergSparkSessionExtensions --conf spark.sql.catalog.rest=org.apache.iceberg.spark.SparkCatalog --conf spark.sql.catalog.rest.type=rest --conf spark.sql.catalog.rest.uri=http://127.0.0.1:9001/iceberg/ --conf spark.sql.catalog.rest.header.X-Iceberg-Access-Delegation=vended-credentials' \
IT_TABLE_IDENTIFIER=rest.ab.a1 \
GRAVITINO_ENV_IT=true \
./gradlew :core:test -PskipIT=true --tests 'org.apache.gravitino.audit.v2.TestCompatibilityUtils'

Risks / follow-ups

• AuditLog.Operation is still shared with legacy audit code, so this change expands the enum surface beyond the legacy formatter coverage.
• If new OperationType values are added later, the new guard test should fail until the mapping is updated.