Use the app artifact in E2E tests (facebook#48444)

Summary:

This change downloads the generated artifact and uses it in the E2E tests

## Context

While looking at the recent failures of the E2E tests, I realized that the Hermes, NewArch, Debug variant often fails to build, not to test, for some misconfiguration.

I also realized that we are already building that varaint successfully once, so why not reuse it? To reuse prebuilds, we need a few steps:

1. make sure we build all the variants we need
2. store the .app file as an artifact
3. download the artifact and use it in the E2E tests

## Changelog:
[Internal] - Build release variant for RNTester

Differential Revision: D67760436

.github/workflows/test-all.yml

@@ -192,10 +192,10 @@ jobs:
           flavor: ${{ matrix.flavor }}
 
   test_e2e_ios_rntester:
-    if: ${{ github.ref == 'refs/heads/main' || contains(github.ref,  'stable') || inputs.run-e2e-tests }}
+    # if: ${{ github.ref == 'refs/heads/main' || contains(github.ref,  'stable') || inputs.run-e2e-tests }}
     runs-on: macos-13-large
     needs:
-      [build_apple_slices_hermes, prepare_hermes_workspace, build_hermes_macos]
+      [test_ios_rntester]
     env:
       HERMES_WS_DIR: /tmp/hermes
       HERMES_TARBALL_ARTIFACTS_DIR: /tmp/hermes/hermes-runtime-darwin
@@ -209,21 +209,17 @@ jobs:
     steps:
       - name: Checkout
         uses: actions/checkout@v4
-      - name: Run it
-        uses: ./.github/actions/test-ios-rntester
+      - name: Download App
+        uses: actions/download-artifact@v4
         with:
-          jsengine: ${{ matrix.jsengine }}
-          architecture: ${{ matrix.architecture }}
-          run-unit-tests: "false"
-          use-frameworks: StaticLibraries
-          hermes-version: ${{ needs.prepare_hermes_workspace.outputs.hermes-version }}
-          react-native-version: ${{ needs.prepare_hermes_workspace.outputs.react-native-version }}
-          run-e2e-tests: "true"
-          flavor: ${{ matrix.flavor }}
+          name: RNTesterApp-${{ matrix.architecture }}-${{ matrix.jsengine }}-${{ matrix.flavor }}
+          path: /tmp/RNTesterBuild/RNTester.app
+      - name: Check downloaded folder content
+        run: ls -lR /tmp/RNTesterBuild
       - name: Run E2E Tests
         uses: ./.github/actions/maestro-ios
         with:
-          app-path: "/tmp/RNTesterBuild/Build/Products/${{ matrix.flavor }}-iphonesimulator/RNTester.app"
+          app-path: "/tmp/RNTesterBuild/RNTester.app"
           app-id: com.meta.RNTester.localDevelopment
           jsengine: ${{ matrix.jsengine }}
           maestro-flow: ./packages/rn-tester/.maestro/