super_errors: round two of error fixture coverage (#8432)

* super_errors: cover typecore Label_not_mutable, Apply_non_function, Invalid_for_loop_index, Field_access_on_dict_type, Private_label

* super_errors: cover typedecl Boxed_and_unboxed, Bad_unboxed_attribute, Constraint_failed

* super_errors: cover translcore Unknown_builtin_primitive and typecore Less_general

* super_errors: cover typemod With_no_component, Cannot_apply, Recursive_module_require_explicit_type

* super_errors: cover translmod Fragile_pattern_in_toplevel and transl_recmodule Circular_dependency

* super_errors: cover includemod signature-mismatch errors (Missing_field, Value_descriptions, Type_declarations)

* super_errors: cover typecore Not_an_extension_constructor, Invalid_extension_constructor_payload, Inlined_record_expected

* super_errors: cover rec_check Illegal_letrec_expr

* super_errors: cover typedecl Nonrec_gadt, Not_extensible_type, Cannot_extend_private_type

* super_errors: cover typedecl Object_spread_with_record_field

* super_errors: cover typetexp Unbound_value, Unbound_constructor, Unbound_label, Unbound_modtype

* super_errors: cover let-module scope escape, typemod Apply_generative and With_mismatch

* super_errors: cover bs_syntaxerr Invalid_bs_int_type, Invalid_bs_string_type, Invalid_bs_unwrap_type

* super_errors: cover bs_syntaxerr Conflict_attributes

* super_errors: cover bs_syntaxerr Expect_string/int_literal and includemod Module_types, Extension_constructors

* super_errors: cover includemod Modtype_infos and typedecl Unbound_type_var_ext

* super_errors: cover typetexp Method_mismatch and typedecl Bad_immediate_attribute

* super_errors: cover typetexp Multiple_constraints_on_type

* super_errors: cover typetexp Access_functor_as_structure, Constructor_mismatch, typedecl Inconsistent_constraint

* super_errors: cover typemod Structure_expected via opening a functor

* super_errors: cover typecore Constructor_arity_mismatch and Private_type construction

* super_errors: cover typemod Not_a_packed_module, typecore Cannot_infer_signature, typedecl Bad_variance

* super_errors: cover typedecl Bad_unboxed_attribute many-fields and extensible cases

* super_errors: cover typedecl Bad_variance contravariant case

* super_errors: cover typetexp Not_an_object and Opened_object via object inheritance

* super_errors: cover typedecl Definition_mismatch and typecore Constructor_arity_mismatch in pattern context

* super_errors: cover typedecl Invalid_attribute for @notUndefined on non-abstract type

* super_errors: cover typedecl Variant_spread_fail when source isn't a variant

* super_errors: cover bs_syntaxerr Not_supported_directive_in_bs_return, Expect_opt_in_bs_return_to_opt, Illegal_attribute

* super_errors: cover typecore Undefined_method via object field access

* super_errors: cover includemod Modtype_permutation

* super_errors: cover typemod Not_allowed_in_functor_body, Incomplete_packed_module, Non_generalizable

* super_errors: cover typetexp Alias_type_mismatch

* Update changelog for #8432