Support JWT auth

[mshustov]

prerequisites:
adjust Cloud integration tests to run them GitHub Actions instance instead of an instance created by the TF provider. JWT-based auth is enabled on the GitHub Actions instance only.

scope:

• ability to attach a JWT token
• ability to overwrite the token on the client instance
• works for both HTTP and TCP connections
• test against ClickHouse Cloud. https://github.com/ClickHouse/clickhouse-js/blob/main/.github/workflows/tests.yml#L218-L220

Reference implementation for HTTP interface:

• nodejs client JWT auth support clickhouse-js#360
• java client [client-v2] Added implementation for Bearer token auth clickhouse-java#1904