[client-v2] Reduce client init time

[chernser]

Summary

This PR intend to reduce time of client init. time.

First problem is that client loads server context on start. This PR is moved it to a public method, so application can run it on demand. Client users are applications that can call this method when it is needed. JDBC will call it after creating a client instance.

Second problem is that SSL context is initialized for clients with only unsecure endpoint. This PR will implement loading SSL context only when it is needed.

SSL context is requires for authentication however it means HTTPS is used at transport protocol.

Checklist

Delete items not relevant to your PR:

• Closes Client.Builder().build() takes 500ms #2032
• Unit and integration tests covering the common scenarios were added
• A human-readable description of the changes was provided to include in CHANGELOG
• For significant changes, documentation in https://github.com/ClickHouse/clickhouse-docs was updated with further explanations or tutorials

[sonarqubecloud]

Quality Gate failed

Failed conditions
70.0% Coverage on New Code (required ≥ 80%)

See analysis details on SonarQube Cloud