SQL autocompletion support

[sunker]

We should add support for syntax highlighting and autcomplete in the Redshift data source. The work

Tasks

• [x] #150
• [x] #153
• [x] #155
• [x] Add default completion item provider to experimental package in the case standard sql is used https://github.com/grafana/grafana-experimental/pull/42
• [x] Support schema in table identifiers https://github.com/grafana/grafana-experimental/pull/43
• [x] #168
• [x] #170
• [x] #172
• [x] Always render new code editor and remove feature flag from Grafana

There are a few things that I don't like about the SQL Editor api in grafana/experimental. For example, functions, operators and supported macros are currently being specified in the autocompletion provider and not in the language. This causes a discrepancy between the syntax highlighting support and the autocompletion support. I'll raise an issue about this in the experimental package so that it can be discusses with the BI squad.

[sunker]

Temporary putting this issue on hold so that I can focus on Grafana 9 critical issues instead

[sarahzinger]

@sunker is it cool if I move this to backlog?

[sunker]

Yes sure!

[vickyyyyyyy]

The Timestream and Athena tickets should be picked up once this is done