Docs for SERVER-38900: Implement JSON Schema parsing for "encrypt"

Description

Description:

Please ping me (Nick) if you have any questions about what to document here. I think it makes sense to include the 'encryptMetadata' keyword in the same DOCS ticket.

Engineering Ticket Description:

• Can be present anywhere in the schema, including top-level.
• Suggest starting with a new "translateEncryptionKeywords" method at the[ entry point in the parser|https://github.com/mongodb/mongo/blob/83a494cb0a1afca5cfaaf9d29eeb8a2ce1e02264/src/mongo/db/matcher/schema/json_schema_parser.cpp#L1355].
• Resulting match expression should contain the new $_internalSchemaBinDataSubType expression.
• This ticket should only implement the parsing required for mongod to understand the new keywords, no mongocryptd/FLE specific logic. For now, require that the "encrypt" argument is an empty object.

Scope of changes

Impact to Other Docs

MVP (Work and Date)

Resources (Scope or Design Docs, Invision, etc.)