Bump deps and min SDKs, move web apps to new bootstrapping logic (#2292)

Also removed the web measurement experiment from the material 3 demo

add_to_app/android_view/flutter_module_using_plugin/pubspec.yaml

@@ -4,7 +4,7 @@ description: An example Flutter module that uses a plugin.
 version: 1.0.0+1
 
 environment:
-  sdk: ^3.3.1
+  sdk: ^3.4.0-0
 
 dependencies:
   flutter:

add_to_app/books/flutter_module_books/pubspec.yaml

@@ -6,7 +6,7 @@ description: A Flutter module using the Pigeon package to demonstrate
 version: 1.0.0+1
 
 environment:
-  sdk: ^3.3.1
+  sdk: ^3.4.0-0
 
 dependencies:
   flutter:

add_to_app/fullscreen/flutter_module/pubspec.yaml

@@ -4,7 +4,7 @@ description: An example Flutter module.
 version: 1.0.0+1
 
 environment:
-  sdk: ^3.3.1
+  sdk: ^3.4.0-0
 
 dependencies:
   flutter:

add_to_app/multiple_flutters/multiple_flutters_module/pubspec.yaml

@@ -4,7 +4,7 @@ description: A module that is embedded in the multiple_flutters_ios and multiple
 version: 1.0.0+1
 
 environment:
-  sdk: ^3.3.1
+  sdk: ^3.4.0-0
 
 dependencies:
   flutter:

add_to_app/plugin/flutter_module_using_plugin/pubspec.yaml

@@ -4,7 +4,7 @@ description: An example Flutter module that uses a plugin.
 version: 1.0.0+1
 
 environment:
-  sdk: ^3.3.1
+  sdk: ^3.4.0-0
 
 dependencies:
   flutter:

add_to_app/prebuilt_module/flutter_module/pubspec.yaml

@@ -4,7 +4,7 @@ description: An example Flutter module.
 version: 1.0.0+1
 
 environment:
-  sdk: ^3.3.1
+  sdk: ^3.4.0-0
 
 dependencies:
   flutter: