QueryTypes: Add feature toggle to show query types in datasource apiservers (#88213)

* initial attempt

* show query types

* show query types

* with formatting

* with formatting

* more cleanup

* add feature toggle

* fix build

pkg/expr/reader.go

@@ -1,7 +1,6 @@
 package expr
 
 import (
-	"embed"
 	"fmt"
 	"strings"
 
@@ -178,13 +177,6 @@ func (h *ExpressionQueryReader) ReadQuery(
 	return eq, err
 }
 
-//go:embed query.types.json
-var f embed.FS
-
-func (h *ExpressionQueryReader) QueryTypeDefinitionListJSON() ([]byte, error) {
-	return f.ReadFile("query.types.json")
-}
-
 func getReferenceVar(exp string, refId string) (string, error) {
 	exp = strings.TrimPrefix(exp, "$")
 	if exp == "" {