Increase the strictness of our requiring explicit types (#7585)

...now that we have generic methods, their types need to be specified too.
diff --git a/.analysis_options b/.analysis_options
index d32449e..0f0e7a8 100644
--- a/.analysis_options
+++ b/.analysis_options
@@ -16,7 +16,8 @@
   language:
     enableStrictCallChecks: true
     enableSuperMixins: true
-  strong-mode: true
+  strong-mode:
+    implicit-dynamic: false
   errors:
     # allow overriding fields (if they use super, ideally...)
     strong_mode_invalid_field_override: ignore