[SR-15841] `CustomNSError` disregards `errorDomain` on `@objc` Error types

[NachoSoto]

Previous ID	SR-15841
Radar	None
Original Reporter	@NachoSoto
Type	Bug

Environment

Xcode Version 13.2.1 (13C100)
swift-driver version: 1.26.21
Apple Swift version 5.5.2 (swiftlang-1300.0.47.5 clang-1300.0.29.30)

Additional Detail from JIRA

Votes	1
Component/s	Compiler, Foundation
Labels	Bug
Assignee	None
Priority	Medium

md5: 2895ace0598550fb916de3edc41de116

Issue Description:

Consider a sample error:

enum E: Int, Error {
    case e1
}

extension E: CustomNSError {
    static let errorDomain: String = "DOMAIN"
}

The following will correctly print "Error DOMAIN:0":

let e = E.e1 as NSError
print("Error \(e.domain):\(e.code)")

However, making the type `@objc` will break this behavior:

@objc(TheError)
enum E: Int, Error {
    case e1
}

extension E: CustomNSError {
    static let errorDomain: String = "DOMAIN"
}

The printed error now becomes:

Error StoreKitTest.E:0

---

A workaround would be to override `_nsErrorDomain`, and while that would work for Swift, the auto-generated `TheErrorDomain` (which comes from the `@objc` name + `Domain`) would still be "StoreKitTest.E` instead of the overridden value.