Expose Unity FastReflection helpers and attribute argument APIs

[annevanede-unity3d]

• Should this pull request have release notes?
  • Yes
  • No
• Do these changes need to be back ported?
  • Yes
  • No
• Do these changes need to be upstreamed to mono/mono or dotnet/runtime repositories?
  • Yes
  • No

Release notes

Mono: Added native APIs to support Unity's FastReflection path — exposes additional class/type/generic helpers via MONO_API, adds non-allocating accessors for custom attribute argument data (mono_unity_get_attr_args_info and friends), a by-pointer variant of mono_unity_generic_class_get_context, an assembly-name C-string helper, and mono_unity_type_is_unmanaged / mono_unity_type_is_blittable_primitive predicates.

Summary of changes

• mono/metadata/unity-utils.h, unity-utils.c:
  • New MonoAttrArgsInfo struct and mono_unity_get_attr_args_info / _free / _type_arg_count / _as_class / _as_int / _as_uint64 / mono_unity_get_attr_type_arg for reading custom attribute constructor arguments without managed allocation.
  • New mono_unity_generic_class_get_context_by_ptr to return MonoGenericContext via out-pointer instead of by value.
  • New mono_unity_class_get_assembly_name_cstring helper.
  • New mono_unity_type_is_blittable_primitive and mono_unity_type_is_unmanaged predicates (the latter inspects fields of non-blittable valuetypes).
  • Promoted several existing helpers to MONO_API: mono_unity_class_get_generic_definition, mono_unity_class_is_array, mono_unity_class_is_class_type, mono_unity_type_is_generic_instance, mono_unity_type_get_generic_class, mono_unity_generic_inst_get_type_argc, mono_unity_generic_inst_get_type_argument.
• mono/metadata/class-internals.h: promote mono_class_has_default_constructor to MONO_API.

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❌ Christopher Redden

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