Add basic runtime tracing (#2996)

This allows us in almost all places to use regions to further trace down
long running tasks.
Also removes an unused function.

internal/tracing_test.go

@@ -0,0 +1,25 @@
+package internal
+
+import (
+	"context"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestTracing(t *testing.T) {
+	inCtx := context.Background()
+
+	task, ctx := StartTask(inCtx, "testing")
+	assert.NotNil(t, ctx)
+	assert.NotNil(t, task)
+	assert.NotEqual(t, inCtx, ctx)
+	task.SetTag("key", "value")
+
+	region, ctx2 := StartRegion(ctx, "testing")
+	assert.NotNil(t, ctx)
+	assert.NotNil(t, region)
+	assert.NotEqual(t, ctx, ctx2)
+	defer task.EndTask()
+	defer region.EndRegion()
+}