CI check generate code (#4998)

* call reflection code generation from tests

This simplifies instructions to contributors so they don't forget to update
reflection code.

* add error handling to generate_code scripts

Let them propagate their errors instead of swallowing them so they show
up when called in CI.

* apply editorconfig to shell scripts

* use ordered map in dart codegen

Using an unordered map in the codegen can lead to spurious diffs in the
generated dart code.

* add CI check for generate_code being run

* update reflection_generated.h

* disable diff-check for monster_test.bfbs

Work around #5008.

.editorconfig

@@ -1,5 +1,5 @@
 root = true
-[*.{cpp,cc,h}]
+[*.{cpp,cc,h,sh}]
 end_of_line = LF
 indent_style = space
 indent_size = 2