[Concurrency] Emit async methods in ObjC protocols once.

[varungandhi-apple]

Previously, the method table would contain duplicate copies due to the
ProtocolDecl carrying a completionHandler-based version of the method,
as well as the async version of the method.

Fixes rdar://76192003.

[varungandhi-apple]

@swift-ci smoke test

[varungandhi-apple]

There is a bug in the current implementation, this will skip methods in @objc protocols written in Swift, not producing an encoding string at all. Fixed by adding a hasClangNode() check.

import Foundation; @objc protocol MyProto { func coolbeans() async -> String }; MyProto.self

// Before
L___unnamed_1:
	.asciz	"_TtP4main7MyProto_"

	.section	__TEXT,__objc_methname,cstring_literals
"L_selector_data(coolbeansWithCompletionHandler:)":
	.asciz	"coolbeansWithCompletionHandler:"

	.section	__TEXT,__cstring,cstring_literals
	.p2align	4
L___unnamed_2:
	.asciz	"v24@0:8@?<v@?@\"NSString\">16"

	.section	__DATA,__objc_data
	.p2align	3
__PROTOCOL_INSTANCE_METHODS__TtP4main7MyProto_:
	.long	24
	.long	1
	.quad	"L_selector_data(coolbeansWithCompletionHandler:)"
	.quad	L___unnamed_2
	.quad	0

	.section	__DATA,__objc_const
	.p2align	3
__PROTOCOL_METHOD_TYPES__TtP4main7MyProto_:
	.quad	L___unnamed_2

// After
L___unnamed_1:
	.asciz	"_TtP4main7MyProto_"

[varungandhi-apple]

@swift-ci smoke test

[atrick]

@varungandhi-apple smoke test only means this blocks @swift-ci test

Concurrency/objc_async_protocol_irgen.swift:15:16: error: CHECK-SAME: is not on the same line as the previous match
// CHECK-SAME: align 8
^
:55:43: note: 'next' match was here
%2 = load atomic i64, i64* %1 monotonic, align 8
^
:28:251: note: previous match ended here
@_PROTOCOL_INSTANCE_METHODS_MyAsyncProtocol = internal constant { i32, i32, [1 x { i8*, i8*, i8* }] } { i32 12, i32 1, [1 x { i8*, i8*, i8* }] [{ i8*, i8*, i8* } { i8* getelementptr inbounds ([15 x i8], [15 x i8]* @"\01L_selector_data(myAsyncMethod:)", i32 0, i32 0), i8* getelementptr inbounds ([11 x i8], [11 x i8]* @1, i32 0, i32 0), i8* null }] }, section "__DATA, __objc_data", align 4
^

Input file:
Check file: /Users/atrick/s/sfix/swift/test/Concurrency/objc_async_protocol_irgen.swift

-dump-input=help explains the following input dump.

Input was:
<<<<<<
.
.
.
50:
51: ; Function Attrs: noinline nounwind readnone
52: define linkonce_odr hidden %swift.type* @__swift_instantiateConcreteTypeFromMangledName({ i32, i32 }* %0) #1 {
53: entry:
54: %1 = bitcast { i32, i32 }* %0 to i64*
55: %2 = load atomic i64, i64* %1 monotonic, align 8
same:15 !~~~~~~ error: match on wrong line
56: %3 = icmp slt i64 %2, 0
57: %4 = call i1 @llvm.expect.i1(i1 %3, i1 false)
58: br i1 %4, label %9, label %5
59:
60: 5: ; preds = %9, %entry

[atrick]

32-bit fix: #36840