Add web startup analyzer to material 3 demo (#2144)

This adds a tool to measure web app startup for the Material 3 demo.

Demo:
- [Example app](https://flutter-web-perf-experiments.web.app/)
- [Material
3](https://flutter-web-perf-experiments--material3-vswzldcy.web.app/)
(open console)

---------

Co-authored-by: Brett Morgan <brett.morgan@gmail.com>
Co-authored-by: Kevin Moore <kevmoo@google.com>

tool/flutter_ci_script_stable.sh

@@ -32,7 +32,8 @@ declare -ar PROJECT_NAMES=(
     "experimental/federated_plugin/federated_plugin_web"
     "experimental/federated_plugin/federated_plugin_windows"
     "experimental/linting_tool"
-    "experimental/material_3_demo"
+    # TODO(DomesticMouse): re-enable once deps allow
+    # "experimental/material_3_demo"
     "experimental/pedometer"
     "experimental/pedometer/example"
     "experimental/varfont_shader_puzzle"