allow using ca_cert parameter

[viktor-ozherelev]

Summary

Relates to the issue. This PR the problem of connecting to a Managed ClickHouse cluster whose server certificate is signed by an internal root Certificate Authority. Added support for the CA root in httpclient and nativeclient using the ca_cert parameter

Checklist

Delete items not relevant to your PR:

• [ ] Unit and integration tests covering the common scenarios were added
• [x] A human-readable description of the changes was provided to include in CHANGELOG

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