This pull request migrates testdata to coreplugin streaming capabilities,
this is mostly a working concept of streaming plugins at the moment,
the work will continue in the following pull requests.
* comes from grafana/gel-app
* remove transform plugin code
* move __expr__ and -100 constants to expr pkg
* set OrgID on request plugin context
* use gtime for resample duration
* in resample, rename "rule" to "window", use gtime for duration, parse duration before exec
* remove gel entry from plugins-bundled/external.json
which creates an empty array for plugins
Refactor to allow shared contract between core and external backend plugins
allowing core backend data sources in Grafana to be implemented in same
way as an external backend plugin.
Use v0.67.0 of sdk.
Add tests for verifying plugin is restarted when process is killed.
Enable strict linting for backendplugin packages
