Guide clients away from withAttributeValues in EncryptionContext

withAttributeValues is OK to be exposed to the SDK via package private or some other means, but clients aren't intended to use it.

The solution we discussed was to deprecate this method. Maybe there is another way to convince clients not to use it.

Locate withAttributeValues in EncryptionContext and inspect how it is exposed and used by the SDK. Review the surrounding API and any existing deprecation guidance or tests before choosing an approach. Done means clients are clearly discouraged from using the method while the SDK can still access the required functionality.

Written by the indexing model from the issue text.