Rules expansion (available via query hints in explore) was broken for expressions that contained selectors.
- fix replacing regexp to recognize `{` and `[` as the end of a rule name
- moved logic to language utils
- added tests
Explore is about keeping context between datasources if possible. When
changing from metrics to logging, some of the filtering can be kept to
narrow down logging streams relevant to the metrics.
- adds `importQueries` function in language providers
- query import dependent on origin datasource
- implemented prometheus-to-logging import: keeping label selectors
that are common to both datasources
- added types
