[client-v2] Added support of reading new JSON as string

[chernser]

Summary

This PR allows reading values from columns of new experimental JSON data type.

• If text base format - then user has to parse a string value to a JSON object. It is available today.
• If Binary format - then user should call getString(columnNameOrIndex) to get string representation of an JSON object and then parse it. This PR just enables reading from JSON typed columns.

It is important to set 2 server settings:

• .serverSetting("allow_experimental_json_type", "1") - to just allow using the new Data Type.
• .serverSetting("output_format_binary_write_json_as_string", "1") - ask server to return JSON as string when one of binary formats is requested.

Note: current PR is to bring essential capability of using JSON as string to the client.

Checklist

Delete items not relevant to your PR:

• 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

[sonarcloud]

Quality Gate failed

Failed conditions
55.2% Coverage on New Code (required ≥ 80%)
C Reliability Rating on New Code (required ≥ A)

See analysis details on SonarCloud

Catch issues before they fail your Quality Gate with our IDE extension SonarLint