Feat(clickhouse): add support for JSONExtractString, clean up some helpers

[georgesittas]

Several changes here, not necessarily related to each other:

• Improve parsing / transpilation of clickhouse's JSONExtractString, fixes Support for Clickhouse JSON Extract* Functions #2051. Note that clickhouse uses 1-based indexing, so I had to slightly change the logic in some parts to take this into account. Perhaps and interesting observation here is that the dialect offset is not necessarily tied to the JSON path offset.
• Refactored some helpers that concern JSON path parsing and generation and are used by clickhouse, postgres, redshift.
• Fixed some issues related to columns being used in json paths (supported by clickhouse, duckdb, postgres). This involved a change that may need some attention in the parser (I split _parse_column into two methods, can elaborate if needed).
• Finally, fixed an issue with multi-arg JSON_EXTRACT calls. It turns out that I had a bug in my implementation and so previously we'd support up to 3 arguments because of the null_if_invalid flag, but 4 would fail. I extended both JSONExtract and JSONExtractScalar to accept arbitrarily many args to amend this.

References:

• https://clickhouse.com/docs/en/sql-reference/functions/json-functions
• https://docs.aws.amazon.com/redshift/latest/dg/JSON_EXTRACT_PATH_TEXT.html