[NT-3070] iOS UI tests in CI

[Alex Freas (akfreas)]

Wires the iOS XCUITest suite into the main pipeline so it runs in parallel with the React Native Android E2E jobs, mirroring the build-once / matrix-run shape of that flow.

• Add a minimal package.json to implementations/ios-sdk/ so it plugs into the existing pnpm run implementation:<name> wrapper, with xcodegen, test:e2e:ios:build:release, and test:e2e:ios:run:release scripts driving xcodebuild build-for-testing and xcodebuild test-without-building
• Add the matching implementation:ios-sdk, setup:e2e:ios-sdk, and test:e2e:ios-sdk root scripts so the iOS flow can be exercised the same way as the JS implementations
• Add an e2e_ios path filter to the changes job covering implementations/ios-sdk/**, lib/mocks/**, and packages/ios/**
• Add e2e-ios-sdk-build (one macOS runner builds both SwiftUI and UIKit schemes into a single DerivedData tree at /tmp/optimization-ios-derived-data and uploads Build/Products as an artifact) and e2e-ios-sdk (matrix scheme: [SwiftUI, UIKit], downloads the artifact back to the same absolute path, boots a simulator, runs the mock server, and invokes test-without-building against the matching .xctestrun)

The first PR runs in smoke mode via IOS_ONLY_TESTING=OptimizationAppUITests<scheme>/PreviewPanelTests so we can validate the artifact round-trip and Namespace macOS runner availability cheaply. A follow-up PR will drop that env var to enable the full suite once green.

Open items to verify on first run:

• Namespace nscloud-macos-arm64-8x32 availability for this org — one-line swap to macos-latest if it's not provisioned
• .xctestrun portability across the split build/test runners — mitigated by using the same absolute path on both, but worth confirming with the first green run