InfluxQLQueryApi.queryJson should not transform all values to String

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__Proposal:__
It would be nice if influxQLQueryApi.queryJson() can preserve field types instead of converting everything to Strings.
ValueExtractor should expose an API with raw types.

__Current behavior:__
Unless a ValueExtractor is present, every values get transformed to String even of the InfluxDB Json result contains a non string value.

__Desired behavior:__
Unless a value extractor is specified, the JSON result should preserve original response types as much as possible

__Alternatives considered:__
For now, provide a value extractor that parse each String values.
It works but doing twice the job: for a number value it get read by Gson as Number then the client converts it to String then manually converted to back to a number.

__Use case:__
All use cases using influxQLQueryApi.

Start at InfluxQLQueryApi.queryJson and trace how ValueExtractor handles values from the InfluxDB JSON response. Check the existing query API behavior and tests, if present, to determine where values are converted to String. Done means queryJson preserves non-string response types by default while still supporting an explicitly provided value extractor.

Written by the indexing model from the issue text.