[stdlib] apply the legacy ABI pattern to 3 functions

Author: glessard

stdlib/public/core/Array.swift

@@ -1601,9 +1601,9 @@ extension Array {
 
   // Superseded by the typed-throws version of this function, but retained
   // for ABI reasons.
+  @_spi(SwiftStdlibLegacyABI) @available(swift, obsoleted: 1)
   @usableFromInline
-  @_disfavoredOverload
-  func withUnsafeBufferPointer<R>(
+  internal func withUnsafeBufferPointer<R>(
     _ body: (UnsafeBufferPointer<Element>) throws -> R
   ) rethrows -> R {
     return try unsafe _buffer.withUnsafeBufferPointer(body)

stdlib/public/core/ArraySlice.swift

@@ -1176,9 +1176,9 @@ extension ArraySlice {
 extension ArraySlice {
   // Superseded by the typed-throws version of this function, but retained
   // for ABI reasons.
+  @_spi(SwiftStdlibLegacyABI) @available(swift, obsoleted: 1)
   @usableFromInline
-  @_disfavoredOverload
-  func withUnsafeBufferPointer<R>(
+  internal func withUnsafeBufferPointer<R>(
     _ body: (UnsafeBufferPointer<Element>) throws -> R
   ) rethrows -> R {
     return try unsafe _buffer.withUnsafeBufferPointer(body)

stdlib/public/core/ContiguousArray.swift

@@ -1118,9 +1118,9 @@ extension ContiguousArray {
 
   // Superseded by the typed-throws version of this function, but retained
   // for ABI reasons.
+  @_spi(SwiftStdlibLegacyABI) @available(swift, obsoleted: 1)
   @usableFromInline
-  @_disfavoredOverload
-  func withUnsafeBufferPointer<R>(
+  internal func withUnsafeBufferPointer<R>(
     _ body: (UnsafeBufferPointer<Element>) throws -> R
   ) rethrows -> R {
     return try unsafe _buffer.withUnsafeBufferPointer(body)

test/api-digester/stability-stdlib-abi-without-asserts.test

@@ -824,6 +824,9 @@ Func _SliceBuffer.withUnsafeMutableBufferPointer(_:) has mangled name changing f
 
 // Functions changed for typed throws
 Constructor Array.init(_unsafeUninitializedCapacity:initializingWith:) has been removed
+Func Array.withUnsafeBufferPointer(_:) has been removed
+Func ArraySlice.withUnsafeBufferPointer(_:) has been removed
+Func ContiguousArray.withUnsafeBufferPointer(_:) has been removed
 
 Struct String.Index has added a conformance to an existing protocol CustomDebugStringConvertible