14719/gauge issues

Fixed new gotmetalinter warning

Don't cut off subsecond precision for postgres macros

Change time format to RFC3339Nano for $__timeFilter, $__timeFrom and
$__timeTo macros

Explore: Remember last used datasource

Fixed issues with panel size in edit mode, fixes #14703

Update yarn.lock

Loki: query limit configurable in datasource

Logs data model: add more log levels

Tweak datetime picker layout for mobile

- use local storage to store last used database
- renamed `datasourceName` property to `initialDatasourceId` for consistency
- adapted tests

only update session in mysql database when required

fix only create/drop database indices if not exists/exists

- add `eror` used in github.com/inconshreveable/log15 (used by Grafana as well)
- add levels from SYSLOG

Loki: change query row to be single field again

Explore: logging UI style fixes

Explore: fix loading indicator z-index on panel container

- existing z-index placed the loading indicator above dropdowns of the panel children
- removed z-index for natural ordering

- tried split selector and search for a week, and it did not feel natural
- keeping some of the original modifications in QueryField from splitting PR
- adapted CheatSheet and placeholder text
- added new label selector state: No labels found

- baseline aligment for meta field labels
- use variables for font sizes and margins

- Loki queries must contain a limit
- this change makes this limit configurable in the datasource
- keep default at 1000, add tooltip on why inc/dec makes sense
- added tests

WIP: makes cache mode configurable

Adds orgId to user dto for provisioned dashboards

Closes the body properly on successful webhooks