[Fonts] Improved icons update script (#88153)

* Improved update_icons.dart

* Handle _

* Update dartdoc

* Rename function

* formatting

* fix type

* Refactor ID generation

* rename

* cleanup

* update comment

* replace typedef with type

dev/tools/pubspec.yaml

@@ -2,7 +2,7 @@ name: dev_tools
 description: Various repository development tools for flutter.
 
 environment:
-  sdk: ">=2.12.0 <3.0.0"
+  sdk: ">=2.13.0 <3.0.0"
 
 dependencies:
   archive: 3.1.2