Provide detailed, path-specific validation errors in MaxMindDatabaseConfig.java

Problem

MaxMindDatabaseConfig.java validates database_paths with
@AssertTrue(message = "database_paths should be S3 URI or HTTP endpoint or local directory")
https://github.com/opensearch-project/data-prepper/blob/f27b493cbace324252c3255555449370cb644595/data-prepper-plugins/geoip-processor/src/main/java/org/opensearch/dataprepper/plugins/geoip/extension/MaxMindDatabaseConfig.java#L43

No matter what is wrong—a nonexistent file, a directory instead of a file, an S3/HTTP URL where a local file is expected, etc.—users always see that single generic line.
Because the validator collapses every error into the same generic message, developers can’t see which specific database_paths entry failed or whether it’s missing, a directory, or an unsupported URI scheme.

Request

Replace the generic message with path-specific feedback, e.g.

Path does not exist: /foo/geoip.mmdb
Directory provided, but a file is required: /data/
S3 URI not allowed here: s3://bucket/geoip.mmdb

Even one clear, detailed message per failing path would make troubleshooting much faster.

Start with data-prepper-plugins/geoip-processor/src/main/java/org/opensearch/dataprepper/plugins/geoip/extension/MaxMindDatabaseConfig.java, especially the database_paths validator around line 43. Review how each path is currently checked and define messages for nonexistent paths, directories, local-file expectations, and unsupported URI schemes. Done means each failing path produces a clear, path-specific validation message instead of the generic text.