Add logging of main actor messages (#110) #189

Job	Run time
list-exercises	4s
validate_course (exercise_000_sudoku_solver_initial_state)	1m 24s
validate_course (exercise_001_dotty_deprecated_syntax_rewriting)	1m 43s
validate_course (exercise_002_dotty_new_syntax_and_indentation_based_syntax)	1m 45s
validate_course (exercise_003_top_level_definitions)	1m 33s
validate_course (exercise_004_parameter_untupling)	1m 38s
validate_course (exercise_005_extension_methods)	1m 27s
validate_course (exercise_006_using_and_summon)	1m 22s
validate_course (exercise_007_givens)	1m 22s
validate_course (exercise_008_enum_and_export)	1m 44s
validate_course (exercise_009_union_types)	1m 38s
validate_course (exercise_010_opaque_type_aliases)	1m 20s
validate_course (exercise_011_multiversal_equality)	1m 39s
validate_course (exercise_020_opaque_type_aliases_alt)	1m 35s
validate_course (exercise_021_multiversal_equality)	1m 24s
validate_course_summary	1s
create_release	0s
	21m 39s

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