Add unified, legacy, and prose tests for CSFLE multi-KMS support.

[vbabanin]

Summary

This PR implements the changes described in the "Downstream Changes Summary" of DRIVERS-2731.

• Updates JavaDoc.
• Implements required spec tests.
• Passes new AWS credentials to test a rewrapManyDataKey with two different AWS accounts using Evergreen expansions: AWS_ACCESS_KEY_ID_2 and AWS_SECRET_ACCESS_KEY_2, configured in the Evergreen Variables page.

NOTE: No changes to the CSFLE API are necessary, as it is forward-compatible because of using Map AutoEncryptionSettings.java#L126). All relevant logic is encapsulated within libmongocrypt. This PR builds on the updated dependency of mongocrypt version 1.10.0-SNAPSHOT which was updated in PR 1406.

Background

Named KMS providers is further described in DBX Scope: Support Named KMS Providers.

The KMS provider identified by a string. Previously supported KMS providers were only: "aws", "azure", "gcp", "kmip", and "local". The KMS provider is now expanded to support name suffixes. (e.g. "local:myname").

Named KMS providers enables more than one of each KMS provider type to be configured.

kms_providers = {
    "local": {"key": local_kek1},        # Unnamed KMS provider.
    "local:myname": {"key": local_kek2 } # Named KMS provider with name "myname".
}

[vbabanin]

A new use-case related to named providers was recently added to the KMS TLS Options specification prose tests. While the existing test testThatCustomSslContextIsUsed for KMS TLS Options does not precisely align with the spec tests, it has been purposefully designed for simplicity achieving the desired effect. In line with the approach discussed in this original comment, this test has been extended to include named providers.