### Godot version

v4.0.rc1.official [8843d9ad3]

### System information

Lubuntu

### Issue description

You can't use + or += to mutate typed arrays.

It seems to be not correctly getting the type information from the second operand.

An erudite poster on the discord puts it differently:
> it's more like operator + doesn't retain Array typing
> the syntax for Array Concatenation via operators, but the idea gets across i think


The error you see is:
```Trying to assign an array of type "Array" to a variable of type "Array[int]".```


### Steps to reproduce

```
	var Alice: Array[int] = [1,2,3]
	var Bob: Array[int] = [4,5,6]
	Alice += Bob
```
This will crash with the above error message.

### Minimal reproduction project

[plus_syntax_broken_demo_project.zip](https://github.com/godotengine/godot/files/10694514/plus_syntax_broken_demo_project.zip)

if (node != nullptr) {
						Ref<GDScript> scr = node->get_script();
						if (scr.is_valid()) {
							Ref<GDScriptParserRef> singl_parser = get_parser_for(scr->get_script_path());
							if (singl_parser.is_valid()) {
								Error err = singl_parser->raise_status(GDScriptParserRef::INHERITANCE_SOLVED);
								if (err == OK) {
									result = type_from_metatype(singl_parser->get_parser()->head->get_datatype());
								}
							}
						}
					}
				}
			}
			result.is_constant = true;
			p_identifier->set_datatype(result);
			return;
		}
	}
	if (CoreConstants::is_global_constant(name)) {
		int index = CoreConstants::get_global_constant_index(name);
		StringName enum_name = CoreConstants::get_global_constant_enum(index);
		int64_t value = CoreConstants::get_global_constant_value(index);
		if (enum_name != StringName()) {
			p_identifier->set_datatype(make_global_enum_type(enum_name, StringName(), false));
		} else {
			p_identifier->set_datatype(type_from_variant(value, p_identifier));
		}
		p_identifier->is_constant = true;
		p_identifier->reduced_value = value;