* (feat/explore): Support for new LogQL filtering syntax
Loki is adding syntax to support chained filtering.
This PR adapts Grafana to support this.
- Send only `query` parameter in loki request
- Automatically wrap search text in simple syntax, e.g., `{} foo` is
sent as `{} |~ "foo"`.
* Adapted to regexp parameter staying on in Loki
* Dont wrap single regexp in new filter syntax
* Fix datasource test
* Fallback regexp parameter for legacy queries
* Fix search highlighting
* Make highlighting work for filter chains
* Fix datasource test
