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

pkg/promlib/querydata/exemplar/sampler_stddev_test.go

@@ -0,0 +1,28 @@
+package exemplar_test
+
+import (
+	"testing"
+	"time"
+
+	"github.com/grafana/grafana-plugin-sdk-go/experimental"
+
+	"github.com/grafana/grafana/pkg/promlib/models"
+	"github.com/grafana/grafana/pkg/promlib/querydata/exemplar"
+)
+
+func TestStdDevSampler(t *testing.T) {
+	sampler := exemplar.NewStandardDeviationSampler().(*exemplar.StandardDeviationSampler)
+	t.Run("standard deviation sampler", func(t *testing.T) {
+		tr := models.TimeRange{
+			Start: time.Unix(0, 0),
+			End:   time.Unix(100000, 0),
+		}
+		ex := generateTestExemplars(tr)
+		sampler.SetStep(600 * time.Second)
+		for i := 0; i < len(ex); i++ {
+			sampler.Add(ex[i])
+		}
+		framer := exemplar.NewFramer(sampler, exemplar.NewLabelTracker())
+		experimental.CheckGoldenJSONFramer(t, "testdata", "stddev_sampler", framer, update)
+	})
+}