Build Release version for RNTester to speed-up E2E (facebook#48443)

Summary:

This change makes sure we build the Release variant of RNTester so we can store the generated app as an artifact and forward it to 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: D67760372

.github/actions/test-ios-rntester/action.yml

@@ -120,14 +120,6 @@ runs:
     - name: Build RNTester
       if: ${{ inputs.run-unit-tests != 'true' && inputs.run-e2e-tests == 'false' }}
       shell: bash
-      run: |
-        xcodebuild build \
-          -workspace packages/rn-tester/RNTesterPods.xcworkspace \
-          -scheme RNTester \
-          -sdk iphonesimulator
-    - name: Build RNTester (E2E Tests)
-      shell: bash
-      if: ${{ inputs.run-e2e-tests == 'true' }}
       run: |
         xcodebuild \
           -scheme "RNTester" \

.github/workflows/test-all.yml

@@ -169,6 +169,14 @@ jobs:
       matrix:
         jsengine: [Hermes, JSC]
         architecture: [NewArch, OldArch]
+        flavor: [Debug, Release]
+        exclude: # We don't want to test the Old Arch in Release for E2E
+          - jsengine: Hermes
+            architecture: OldArch
+            flavor: Release
+          - jsengine: JSC
+            architecture: OldArch
+            flavor: Release
     steps:
       - name: Checkout
         uses: actions/checkout@v4
@@ -181,6 +189,7 @@ jobs:
           use-frameworks: StaticLibraries
           hermes-version: ${{ needs.prepare_hermes_workspace.outputs.hermes-version }}
           react-native-version: ${{ needs.prepare_hermes_workspace.outputs.react-native-version }}
+          flavor: ${{ matrix.flavor }}
 
   test_e2e_ios_rntester:
     if: ${{ github.ref == 'refs/heads/main' || contains(github.ref,  'stable') || inputs.run-e2e-tests }}