feat(medusa): Rollout index engine behind feature flag (#11431)

**What**
- Add index engine feature flag
- apply it to the `store/products` end point as well as `admin/products`
- Query builder various fixes
- search capabilities on full data of every entities. The `q` search will be applied to all involved joined table for selection/where clauses

Co-authored-by: Carlos R. L. Rodrigues <37986729+carlos-r-l-rodrigues@users.noreply.github.com>

packages/modules/index/integration-tests/__tests__/query-builder.spec.ts

@@ -414,7 +414,19 @@ describe("IndexModuleService query", function () {
       },
     })
 
+    // NULLS LAST (DESC = first)
     expect(data).toEqual([
+      {
+        id: "prod_2",
+        title: "Product 2 title",
+        deep: {
+          a: 1,
+          obj: {
+            b: 15,
+          },
+        },
+        variants: [],
+      },
       {
         id: "prod_1",
         variants: [
@@ -440,17 +452,6 @@ describe("IndexModuleService query", function () {
           },
         ],
       },
-      {
-        id: "prod_2",
-        title: "Product 2 title",
-        deep: {
-          a: 1,
-          obj: {
-            b: 15,
-          },
-        },
-        variants: [],
-      },
     ])
 
     const { data: dataAsc } = await module.query({
@@ -469,17 +470,6 @@ describe("IndexModuleService query", function () {
     })
 
     expect(dataAsc).toEqual([
-      {
-        id: "prod_2",
-        title: "Product 2 title",
-        deep: {
-          a: 1,
-          obj: {
-            b: 15,
-          },
-        },
-        variants: [],
-      },
       {
         id: "prod_1",
         variants: [
@@ -505,6 +495,17 @@ describe("IndexModuleService query", function () {
           },
         ],
       },
+      {
+        id: "prod_2",
+        title: "Product 2 title",
+        deep: {
+          a: 1,
+          obj: {
+            b: 15,
+          },
+        },
+        variants: [],
+      },
     ])
   })
 
@@ -565,6 +566,11 @@ describe("IndexModuleService query", function () {
       pagination: {
         take: 100,
         skip: 0,
+        order: {
+          product: {
+            created_at: "ASC",
+          },
+        },
       },
     })
 
@@ -596,7 +602,7 @@ describe("IndexModuleService query", function () {
           product: {
             variants: {
               prices: {
-                amount: "DESC",
+                amount: "ASC",
               },
             },
           },
@@ -608,14 +614,14 @@ describe("IndexModuleService query", function () {
       {
         id: "prod_1",
         variants: [
-          {
-            id: "var_1",
-            sku: "aaa test aaa",
-          },
           {
             id: "var_2",
             sku: "sku 123",
           },
+          {
+            id: "var_1",
+            sku: "aaa test aaa",
+          },
         ],
       },
       {