Add mongo datapoints for encryption

Testing mongodb_exporter
You can find FB here https://github.com/Percona-Lab/pmm-submodules/pull/2948

There will should appear new metric `mongodb_security_encryption_enabled` for MongoDB which are encrypted. Use next configuration for setuping MongoDB in different modes:

1. MongoDB enterprise Encrypted with Local file - https://github.com/implex-p6/pmm-test-infra/tree/master/mongo-setup/enterprise_standalone_encrypted. Metric should be  equal to `mongodb_security_encryption_enabled{type="localKeyFile"}`

2. MongoDB enterprise Encrypted with KMIP. - https://github.com/implex-p6/pmm-test-infra/tree/master/mongo-setup/enterprise_standalone_encrypted_kmip_server. Metric should be  equal to `mongodb_security_encryption_enabled{type="kmip"}`

3. Percona MongoDB encrypted using Vault - https://github.com/implex-p6/pmm-test-infra/tree/master/mongo-setup/pmdb_standalone_encrypted_vault Metric should be  equal to`mongodb_security_encryption_enabled{type="vault"}`

Testing sending metrics
You can find FB here https://github.com/Percona-Lab/pmm-submodules/pull/2966
There should be added two new metrics:

• mongodb_encryption_at_rest_enabled - shows whether encryption at rest is enabled on the mongodb instance or not

• mongodb_encryption_at_rest_type - shows the type of the encrytpion. If monogdb doesn't have enabled encryption this metric should not exist.

Setup for mongodb you can find here: https://github.com/implex-p6/pmm-test-infra/tree/master/mongo-setup
Charts you can find here: https://pmm.check-dev.percona.com/graph/d/v1czpTp4z/pmm-telemetry-panels-library-mongo?orgId=1&from=now-30d&to=now