Prometheus: Introduce prometheus backend library (#83952)

* Move files to prometheus-library

* refactor core prometheus to use prometheus-library

* modify client transport options

* mock

* have a type

* import aliases

* rename

* call the right method

* remove unrelated test from the library

* update codeowners

* go work sync

* update go.work.sum

* make swagger-clean && make openapi3-gen

* add promlib to makefile

* remove clilogger

* Export the function

* update unit test

* add prometheus_test.go

* fix mock type

* use mapUtil from grafana-plugin-sdk-go

.github/CODEOWNERS

@@ -105,6 +105,7 @@
 /pkg/server/ @grafana/backend-platform
 /pkg/apiserver @grafana/grafana-app-platform-squad
 /pkg/apimachinery @grafana/grafana-app-platform-squad
+/pkg/promlib @grafana/observability-metrics
 /pkg/services/annotations/ @grafana/backend-platform
 /pkg/services/apikey/ @grafana/identity-access-team
 /pkg/services/cleanup/ @grafana/backend-platform