Chore: Expression engine to support relative time range (#57474)

* make TimeRange interface and add relative range
* make Execute methods support the current time
* update resample to support relative time range
* update DSNode to support relative time range
* update query service to create queries with absolute time
* make alerting evaluator create relative time ranges

pkg/expr/classic/classic.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"strconv"
+	"time"
 
 	"github.com/grafana/grafana-plugin-sdk-go/data"
 
@@ -67,7 +68,7 @@ func (cmd *ConditionsCmd) NeedsVars() []string {
 
 // Execute runs the command and returns the results or an error if the command
 // failed to execute.
-func (cmd *ConditionsCmd) Execute(_ context.Context, vars mathexp.Vars) (mathexp.Results, error) {
+func (cmd *ConditionsCmd) Execute(_ context.Context, _ time.Time, vars mathexp.Vars) (mathexp.Results, error) {
 	firing := true
 	newRes := mathexp.Results{}
 	noDataFound := true

pkg/expr/classic/classic_test.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"encoding/json"
 	"testing"
+	"time"
 
 	"github.com/grafana/grafana-plugin-sdk-go/data"
 	"github.com/stretchr/testify/require"
@@ -405,7 +406,7 @@ func TestConditionsCmdExecute(t *testing.T) {
 
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
-			res, err := tt.conditionsCmd.Execute(context.Background(), tt.vars)
+			res, err := tt.conditionsCmd.Execute(context.Background(), time.Now(), tt.vars)
 			require.NoError(t, err)
 
 			require.Equal(t, 1, len(res.Values))