Merge branch 'CDRIVER-2153-pool-ssl'

* CDRIVER-2153-pool-ssl:
  CDRIVER-2153 Install our custom CA to the system trust store
  CDRIVER-2153 Add SNI support for the mock server
  CDRIVER-2153 mongoc_client_pool_t cannot connect to MongoDB Atlas
  CDRIVER-2154 SNI not provided when allow_invalid_hostname is set