Make MongoDB schema scripts idempotent

[answndud]

Summary

• make the MongoDB schema scripts idempotent by using upserts for sequence initialization
• create MongoDB indexes through the JSONL script so rerunning the script keeps the schema in place without resetting state
• add integration coverage for applying the MongoDB creation script twice and verifying sequence values keep increasing

Testing

• ./mvnw -pl spring-batch-core -Dtest=MongoDBSchemaScriptsIntegrationTests test
• Local verification is currently blocked before test execution because this environment does not provide JDK 22 for the projects NullAway JSpecify configuration.

Closes #5328