Emit Objective-C resilient class stubs for concrete subclasses of generic subclasses of NSObject

[slavapestov]

Fixes rdar://problem/71194117.

[slavapestov]

@swift-ci Please smoke test

[xedin]

@slavapestov @shahmishal New test which has added by this PR fails on iphonesimulator-i386:

00:13:08 --
00:13:08 /Volumes/swift-ci/jenkins/workspace/oss-swift_tools-R_stdlib-RD_test-simulator/swift/test/IRGen/Inputs/Foundation.swift:110:13: warning: all paths through this function will call itself
00:13:08 public func _convertErrorToNSError(_ error: Error) -> NSError {
00:13:08             ^
00:13:08 /Volumes/swift-ci/jenkins/workspace/oss-swift_tools-R_stdlib-RD_test-simulator/swift/test/IRGen/objc_generic_class_stub.swift:17:17: error: CHECK-LABEL: expected string not found in input
00:13:08 // CHECK-LABEL: @"$s23objc_generic_class_stub24ConcreteNSObjectSubclassCMt" = internal global %objc_full_class_stub { i64 0, i64 1, %objc_class* (%objc_class*, i8*)* @"$s23objc_generic_class_stub24ConcreteNSObjectSubclassCMU" }
00:13:08                 ^
00:13:08 <stdin>:1:1: note: scanning from here
00:13:08 ; ModuleID = '<swift-imported-modules>'
00:13:08 ^
00:13:08 
00:13:08 Input file: <stdin>
00:13:08 Check file: /Volumes/swift-ci/jenkins/workspace/oss-swift_tools-R_stdlib-RD_test-simulator/swift/test/IRGen/objc_generic_class_stub.swift
00:13:08 
00:13:08 -dump-input=help explains the following input dump.
00:13:08 
00:13:08 Input was:
00:13:08 <<<<<<
00:13:08           1: ; ModuleID = '<swift-imported-modules>'
00:13:08 label:17     X~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ error: no match found
00:13:08           2: source_filename = "<swift-imported-modules>"
00:13:08 label:17     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
00:13:08           3: target datalayout = "e-m:o-p:32:32-p270:32:32-p271:32:32-p272:64:64-f64:32:64-f80:128-n8:16:32-S128"
00:13:08 label:17     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
00:13:08           4: target triple = "i386-apple-ios7.0.0-simulator"
00:13:08 label:17     ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
00:13:08           5: 
00:13:08 label:17     ~
00:13:08           6: %0 = type opaque
00:13:08 label:17     ~~~~~~~~~~~~~~~~
00:13:08           .
00:13:08           .
00:13:08           .
00:13:08 >>>>>>
00:13:08 
00:13:08 --
00:13:08 
00:13:08 ********************

[xedin]

This is the full test build where this PR has been included - https://ci.swift.org/job/oss-swift_tools-R_stdlib-RD_test-simulator/5642