Add support for InfluxDB's time zone clause

[jkreileder]

This fixes #10322 by adding support for Influx DB's time zone clause.

[jangaraj]

I would like to have an option to use dashboard timezone. It will be useful, especially if dashboard uses browser time zone.

[jkreileder]

Good idea but probably not in the scope of the issue and this pull request as it is a more global thing:
You can get the browser's timezone with Intl.DateTimeFormat().resolvedOptions().timeZone but this should be made available for all of Grafana and not just the influxdb plug-in.

(My use case is actually the other way round, I want Grafana panels to use the timezone of the data. This pull requests is one step required for that. The other is #558; I'll probably make a pull request for that sometime soon.)

[rmiggily]

Finally! A feature to resolve all the time zone related headaches of InfluxDB! Thanks for your commit. Could somebody please merge this change?

[cykl]

Any blocker? These 20 LOCs are super useful. How can I help to get them merged?

[blalor]

Are there any blockers to getting this merged? I'd really like to have this feature!

[cby016]

+1 for this feature

[cykl]

@torkelo I apologize for the direct ping, but this PR has been stalled since this summer without any positive or negative feedback from Grafana team. How can we move forward?

I just tested this PR against v5.4.1 and InfluxDB 1.6.0. Works for me.

[torkelo]

Sorry for lack of feedback. Think it needs some UX changes to it does not take up space in the query editor when not used (similar to some other option that can be added via the plus button after group by).

Also needs corresponding backend update (influxdb code in backend go code)

[torkelo]

Another PR (that was a continuation on this PR, #14627) was now merged!

Thank you for contributing to Grafana!

[rmiggily]

@torkelo Thanks for your time.