MONGOCRYPT-771 Remove check for $jsonSchema siblings

[kevinAlbs]

Summary

Do not error if remote $jsonSchema has sibling fields.

Background & Motivation

When processing a response to listCollections, libmongocrypt only checks the response for a top-level $jsonSchema within validator.

libmongocrypt errors if the $jsonSchema has sibling fields and query analysis (mongocryptd/crypt_shared) indicates the JSON Schema has encrypted fields:

db.command({
    "create": "coll",
    "validator": {
        "$jsonSchema": csfle_schema, # Defines 'secret' as encrypted.
        "secret": "foo" # Sibling validator contradicts the JSON schema.
    }
})

encrypted_db["coll"].find_one({}) # Error: schema requires encryption, but collection JSON schema validator has siblings

The spec says this of the motivation:

If we allow siblings, we can run into cases where the user specifies a top-level $and/$or or any arbitrary match-expression that could have nested $jsonSchema's.

However, this check seems incomplete. A validator can have a single top-level JSON schema keyword, and reference encrypted fields:

db.command({
    "create": "coll",
    "validator": {
        "$or": [{"$jsonSchema": csfle_schema}, {"foo": "bar"}]
    }
})

encrypted_db["coll"].insert_one({"secret": "blah", "foo": "bar"}) # libmongocrypt ignores $jsonSchema.
self.assertEqual (db["coll"].find_one()["secret"], "blah") # Unencrypted!

And this check can error in valid cases:

db.command({
    "create": "coll",
    "validator": {
        "$jsonSchema": csfle_schema, # Defines 'secret' as encrypted.
        "unrelated": "foo" # Sibling validator does not contradict the JSON schema.
    }
})

with self.assertRaises(EncryptionError) as ctx:
    encrypted_db["coll"].find_one({})
self.assertIn("schema requires encryption, but collection JSON schema validator has siblings", str(ctx.exception))

I do not expect this check is useful. If a $jsonSchema has sibling fields that contradict the $jsonSchema, I expect that is a misconfiguration that would be discovered soon after attempting to insert data. If the siblings do not contradict the JSON Schema, then there is no reason to error.

Related to: #947, query analysis 8.1 supports a new field csfleEncryptionSchemas to accept multiple JSON Schemas. The replied schemaRequiresEncryption only indicates if any of the sent schemas require encryption. Multiple schemas further complicates this check (I.e. if libmongocrypt gets "schemaRequiresEncryption": true it does not know which of the JSON Schemas required encryption).

[rcsanchez97]

LGTM