Prometheus: Fix Instant query time calculation (#60815)
* Use single point in time instead of doing time range calculation
* Comment update
(cherry picked from commit 15d32546ea)
Prometheus: Add POST support to client (#60243)
* Prometheus: Add POST support to client
* Prometheus: Revert client test change from 1c503908
(cherry picked from commit 055c3b7332)
Co-authored-by: Fionera <fionera@fionera.de>
* Sent resource calls for metadata to the backend
* moved resource calls to the backend
* code review feedback
* fixed post with body
* statuscode >= 300
* cleanup
* fixed tests
* fixed datasource tests
* code review feedback
* force some other endpoints to only GET
* fix linting errors
* fixed tests
* was able to remove section of redundant code
* cleanup and code review feedback
* moved query_exemplars to get request
* fixed return on error
* went back to resource calls, but using the backendsrv directly
* moved to a resource call with fallback
* fixed tests
* check for proper messages
* proper check for invalid calls
* code review changes
