* tsdb: add support for setting debug flag of tsdb query

* alerting: adds debug flag in eval context

Debug flag is set when testing an alert rule and this debug
flag is used to return more debug information in test aler rule
response. This debug flag is also provided to tsdb queries so
datasources can optionally add support for returning additional
debug data

* alerting: improve test alert rule ui

Adds buttons for expand/collapse json and copy json to clipboard,
very similar to how the query inspector works.

* elasticsearch: implement support for tsdb query debug flag

* elasticsearch: embedding client response in struct

* alerting: return proper query model when testing rule