fix: example iOS SPM build and apply Flutter 3.44 example migrations

[muzahidul-opti]

Summary

 example/ios/Runner.xcodeproj  Flutter group
-  optimizely_flutter_sdk -> ../../ios/optimizely_flutter_sdk   # folder ref (added in #116)
   FlutterFramework
   FlutterGeneratedPluginSwiftPackage

Xcode treats a package folder added to a project as a local override, and it uses the folder name as the package identity (optimizely_flutter_sdk). Flutter's generated plugin package points at the same package through a symlink named optimizely-flutter-sdk. SPM won't let one package have two identities:

unable to override package 'optimizely_flutter_sdk' because its identity
'optimizely-flutter-sdk' doesn't match override's identity (directory name) 'optimizely_flutter_sdk'

Also commits the project migrations Flutter 3.44 applies on every flutter build/analyze. Without them, every build leaves the example with uncommitted changes:

 example/ios/Runner/AppDelegate.swift
-  class AppDelegate: FlutterAppDelegate
-    GeneratedPluginRegistrant.register(with: self)
+  class AppDelegate: FlutterAppDelegate, FlutterImplicitEngineDelegate
+    didInitializeImplicitFlutterEngine → GeneratedPluginRegistrant.register(with: engineBridge.pluginRegistry)
 example/ios/Runner/Info.plist
+  UIApplicationSceneManifest → FlutterSceneDelegate (UIScene lifecycle)
 example/analysis_options.yaml
+  analyzer.exclude: build/, android/, ios/, web/, windows/, macos/, linux/

Removing the folder reference leaves Flutter's generated package as the only reference to the plugin. You can still browse and edit the plugin sources through that package in Xcode.

Evidence

• Before (master, checkout folder optimizely-flutter-sdk): cd example && flutter build ios --simulator --no-codesign → exit 1, the identity error above.
  After (this branch, same folder name): ✓ Built build/ios/iphonesimulator/Runner.app → exit 0.
• Migrations: before, flutter build ios left 3 modified files. After, rebuilding leaves git status clean, and the build still passes.
• cd example && flutter analyze: 85 issues both before and after. All are existing prefer_const_constructors-style info lints, and none come from this PR.

Merge Danger

Door: two-way. Revert the two removed lines.
Blast Radius: example app only. The UIScene migration changes how the example registers plugins, following Flutter's own template. It isn't part of the pub.dev package, and CI doesn't build it. No effect on SDK consumers.

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