Provide timezone in the IANA specification

The driver will detect system's set time zone (or that set through an environment variable) and provide that to Elasticsearch in the ISO 8601 UTC offset format `±[hh]:[mm]`. This however doesn't convey DST rules that should be applied on the server when processing dates. This is particularity relevant for the [date histogram agg](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-aggregations-bucket-datehistogram-aggregation.html), used by SQL's [HISTOGRAM](https://www.elastic.co/guide/en/elasticsearch/reference/master/sql-functions-grouping.html#sql-functions-grouping-histogram) grouping function.

This issue is to enhance driver's functionality to allow the timezones be specified using the IANA format, which convey the DST rules to apply based on a timestamp's value.