remove hardcoded $__timeFilter, make macros functional in where clause

public/app/plugins/datasource/postgres/sql_part.ts

@@ -115,6 +115,16 @@ register({
   renderer: columnRenderer,
 });
 
+register({
+  type: 'macro',
+  style: 'function',
+  label: 'Macro:',
+  addStrategy: addExpressionStrategy,
+  params: [],
+  defaultParams: [],
+  renderer: columnRenderer,
+});
+
 register({
   type: 'aggregate',
   style: 'label',