InfluxDB: annotations migration to backend

[joey-grafana]

What this PR does / why we need it:
Part of #43076

This PR contains the changes needed to migrate annotations to the backend.

Test scenarios:

1. Run make devenv sources=influxdb,influxdb1,grafana grafana_version=8.2.4 (or other version before changes)
2. Open up http://localhost:3000 && http://127.0.0.1:3001 (to test older 8.2.4 version)
3. Select gdev-influxdb-influxql
   • create a dashboard
   • create an annotation query in your dashboard e.g. select * from logs where time >= now() - 30m and time <= now() (be careful with the - 30m above as setting a value too big will potentially return tens of thousands of results. Maybe a smaller time like - 10m to start and increment until you get a number of results you are happy with)
   • add a time series panel hooked up to influxdb
   • set time range to last 3 hours or so (at least enough to cover time range set on annotation query)
   • go back to your dashboard and toggle on the annotation query -> you should see annotations in your dashboard
   • go back to your panel in edit mode -> you should see annotations
4. Select gdev-influxdb1-influxql
   • Should behave like gdev-influxdb-influxql

PS: make sure
[feature_toggles]
enable = influxdbBackendMigration

[yesoreyeram]

Field mapping doesn't seems to work correctly after migration. Example For the query SELECT time,host,message,path from logs where time >= now() - 30m and time <= now(), the tags are not working as expected after migration.

Query:

Before migration:

After migration:

[yesoreyeram]

Also there are chances that user have multiple fields as tags.

[joey-grafana]

[yesoreyeram]

Can we add tests for field migration as well? especially for tags?

[yesoreyeram]

LGTM