Unistore Chore: Add OTEL testing harness (#94835)

* add testing harness

* fix mockery and linters

* fix data race in tests

* fix data race in tests

* reduce cardinality of data

pkg/storage/unified/sql/db/mocks/util.go

@@ -0,0 +1,56 @@
+package mocks
+
+import (
+	"reflect"
+	"testing"
+
+	mock "github.com/stretchr/testify/mock"
+)
+
+func NewRowWithValues(t *testing.T, values ...any) *Row {
+	row := NewRow(t)
+	row.EXPECT().Err().Return(nil).Once() // should check error
+	ExpectRowValues(t, row, values...)
+	return row
+}
+
+func ExpectRowValues(t *testing.T, row *Row, values ...any) *Row_Scan_Call {
+	return row.EXPECT().Scan(mock.Anything).RunAndReturn(func(dsts ...any) error {
+		scan(t, dsts, values)
+		return nil
+	})
+}
+
+func scan(t *testing.T, dsts, srcs []any) {
+	t.Helper()
+	if len(dsts) > len(srcs) {
+		t.Fatalf("%d destination values, but only %d source values", len(dsts),
+			len(srcs))
+		return
+	}
+
+	for i := range dsts {
+		src := reflect.ValueOf(srcs[i])
+		if !src.IsValid() {
+			t.Fatalf("%d-eth value to be returned by the mocked db is"+
+				" invalid: %#v", i, srcs[i])
+			return
+		}
+
+		dst := reflect.ValueOf(dsts[i])
+		if !dst.IsValid() || dst.Kind() != reflect.Pointer {
+			t.Fatalf("%d-eth argument passed to Scan is invalid or not"+
+				" a pointer: %#v", i, dsts[i])
+			return
+		}
+
+		dst = dst.Elem() // get element to which the pointer points to
+		if !dst.CanSet() || !src.Type().AssignableTo(dst.Type()) {
+			t.Fatalf("%d-eth destination cannot be set, orcannot be assigned "+
+				"the value; type of destination: %T; value that would be "+
+				"assigned: %#v", i, dsts[i], srcs[i])
+			return
+		}
+		dst.Set(src)
+	}
+}