Update some missing reflection availability (#63087)

Author: Azoy

stdlib/public/Reflection/Sources/_Runtime/ConformanceDescriptor.swift

@@ -11,7 +11,7 @@
 
 import Swift
 
-@available(SwiftStdlib 9999, *)
+@available(SwiftStdlib 5.9, *)
 @frozen
 public struct ConformanceDescriptor: PublicLayout {
   public typealias Layout = (
@@ -29,7 +29,7 @@ public struct ConformanceDescriptor: PublicLayout {
   }
 }
 
-@available(SwiftStdlib 9999, *)
+@available(SwiftStdlib 5.9, *)
 extension ConformanceDescriptor {
   @inlinable
   public var `protocol`: ProtocolDescriptor {

stdlib/public/Reflection/Sources/_Runtime/ExistentialContainer.swift

@@ -11,7 +11,7 @@
 
 import Swift
 
-@available(SwiftStdlib 9999, *)
+@available(SwiftStdlib 5.9, *)
 @frozen
 public struct AnyExistentialContainer {
   public typealias Storage = (
@@ -38,7 +38,7 @@ public struct AnyExistentialContainer {
   }
 }
 
-@available(SwiftStdlib 9999, *)
+@available(SwiftStdlib 5.9, *)
 extension AnyExistentialContainer {
   @inlinable
   public mutating func allocateBox(_ body: (UnsafeMutableRawPointer) -> ()) {
@@ -80,7 +80,7 @@ extension AnyExistentialContainer {
   }
 }
 
-@available(SwiftStdlib 9999, *)
+@available(SwiftStdlib 5.9, *)
 @frozen
 public struct ExistentialContainer {
   public typealias Storage = (
@@ -92,7 +92,7 @@ public struct ExistentialContainer {
   var storage: Storage
 }
 
-@available(SwiftStdlib 9999, *)
+@available(SwiftStdlib 5.9, *)
 @inlinable
 public func container(for box: Any) -> AnyExistentialContainer {
   unsafeBitCast(box)

stdlib/public/Reflection/Sources/_Runtime/Functions.swift

@@ -12,7 +12,7 @@
 import Swift
 import _SwiftRuntimeShims
 
-@available(SwiftStdlib 9999, *)
+@available(SwiftStdlib 5.9, *)
 @frozen
 public struct BoxPair {
   public typealias Storage = (
@@ -34,11 +34,11 @@ public struct BoxPair {
   }
 }
 
-@available(SwiftStdlib 9999, *)
+@available(SwiftStdlib 5.9, *)
 @_silgen_name("swift_allocBox")
 public func swift_allocBox(_: Metadata) -> BoxPair
 
-@available(SwiftStdlib 9999, *)
+@available(SwiftStdlib 5.9, *)
 @inlinable
 public func swift_conformsToProtocol(
   _ type: Metadata,
@@ -51,7 +51,7 @@ public func swift_conformsToProtocol(
   return WitnessTable(wt)
 }
 
-@available(SwiftStdlib 9999, *)
+@available(SwiftStdlib 5.9, *)
 @inlinable
 public func swift_projectBox(
   _ obj: HeapObject

stdlib/public/Reflection/Sources/_Runtime/HeapObject.swift

@@ -11,7 +11,7 @@
 
 import Swift
 
-@available(SwiftStdlib 9999, *)
+@available(SwiftStdlib 5.9, *)
 @frozen
 public struct HeapObject: PublicLayout {
   public typealias Layout = (
@@ -27,7 +27,7 @@ public struct HeapObject: PublicLayout {
   }
 }
 
-@available(SwiftStdlib 9999, *)
+@available(SwiftStdlib 5.9, *)
 extension HeapObject {
   @inlinable
   public var type: Metadata {

stdlib/public/Reflection/Sources/_Runtime/WitnessTable.swift

@@ -11,7 +11,7 @@
 
 import Swift
 
-@available(SwiftStdlib 9999, *)
+@available(SwiftStdlib 5.9, *)
 @frozen
 public struct WitnessTable: PublicLayout {
   public typealias Layout = ConformanceDescriptor