perf: avoid unnecessary data router re-renders (#15376)

Author: brophdawg11

packages/react-router/.changes/patch.reduce-data-router-renders.md

@@ -0,0 +1,3 @@
+Switch to more granular internal router contexts to avoid unnecessary route component re-renders when unrelated data router state changes
+
+- ⚠️ This contains some breaking changes to exported `UNSAFE_` contexts, so please review carefully if you are using those unsafe exports

packages/react-router/__tests__/data-memory-router-test.tsx

@@ -797,15 +797,7 @@ describe("createMemoryRouter", () => {
 
     spy.mockClear();
     fireEvent.click(screen.getByText("Link to Bar"));
-    expect(spy).toHaveBeenCalledWith("Layout", [
-      {
-        data: undefined,
-        handle: undefined,
-        id: "0",
-        params: {},
-        pathname: "/",
-      },
-    ]);
+    expect(spy).not.toHaveBeenCalled();
 
     spy.mockClear();
     await waitFor(() => screen.getByText("Bar"));