feat(index): Provide a similar API to Query (#9193)

**What**
Align the index engine API to be similar to the Query API

## Example

```ts
        // Benefit from the same level of typing like the remote query

        const { data, metadata } = await indexEngine.query<'product'>({
          fields: [
            "product.*",
            "product.variants.*",
            "product.variants.prices.*",
          ],
          filters: {
            product: {
              variants: {
                prices: {
                  amount: { $gt: 50 },
                },
              },
            },
          },
          pagination: {
            order: {
              product: {
                variants: {
                  prices: {
                    amount: "DESC",
                  },
                },
              },
            },
          },
        })
```

packages/modules/index/src/utils/__tests__/flatten-object-keys.spec.ts

@@ -0,0 +1,29 @@
+import { flattenObjectKeys } from "../flatten-object-keys"
+
+describe("flattenWhereClauses", () => {
+  it("should flatten where clauses", () => {
+    const where = {
+      a: 1,
+      b: {
+        c: 2,
+        d: 3,
+        z: {
+          $ilike: "%test%",
+        },
+        y: null,
+      },
+      e: 4,
+    }
+
+    const result = flattenObjectKeys(where)
+
+    expect(result).toEqual({
+      a: 1,
+      "b.c": 2,
+      "b.d": 3,
+      "b.z": { $ilike: "%test%" },
+      "b.y": null,
+      e: 4,
+    })
+  })
+})

packages/modules/index/src/utils/__tests__/normalize-fields-selcetion.spec.ts

@@ -0,0 +1,22 @@
+import { normalizeFieldsSelection } from "../normalize-fields-selection"
+
+describe("normalizeFieldsSelection", () => {
+  it("should normalize fields selection", () => {
+    const fields = [
+      "product.id",
+      "product.title",
+      "product.variants.*",
+      "product.variants.prices.*",
+    ]
+    const result = normalizeFieldsSelection(fields)
+    expect(result).toEqual({
+      product: {
+        id: true,
+        title: true,
+        variants: {
+          prices: true,
+        },
+      },
+    })
+  })
+})