Issue #, if available:

Description of changes:

• Block shared cache for Searchable Encryption / Beacons
• Tested this by running complex beacon example in Rust with MultiKeyStore and shared cache by updating beacon_config.rs. Error:

thread 'main' panicked at src/intercept.rs:88:63:
called `Result::unwrap()` on an `Err` value: DynamoDbEncryptionError { error: DynamoDbEncryptionException { message: "Scan Beacons and Searchable Encryption do NOT support Shared caches." } }
note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace

Resolved through #1507

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