[C++][Parquet] KMS URL pass-through should be configurable #51349

If a user hasn't configured the KMS URL in their KmsConnectionConfig, it will be read from metadata embedded in the Parquet file (in GetKmsClientFromConfigOrKeyMaterial). This means an attacker could craft a Parquet file with the KMS URL set to a host they control, and if the user's KMS client implementation doesn't validate the received URL, it might send an access token to that URL, unintentionally exposing it.

Whether a KMS URL is passed-through from file key material to the KMS client configuration when reading Parquet should be configurable and disabled by default. Users should have to opt-in to this, thereby acknowledging that they are responsible for validating the KMS URL if they enable this.

This same issue has been addressed in Java Parquet (see apache/parquet-java#3745 and https://lists.apache.org/thread/ro2vomk9xxhv34xhvopgys96c9j8ojm0).