[stdlib] update copyBytes with primary associated type

Author: glessard

stdlib/public/core/UnsafeBufferPointerSlice.swift

@@ -26,9 +26,7 @@ extension Slice where Base == UnsafeMutableRawBufferPointer {
   ///   be less than or equal to this buffer slice's `count`.
   @inlinable
   @_alwaysEmitIntoClient
-  public func copyBytes<C: Collection>(
-    from source: C
-  ) where C.Element == UInt8 {
+  public func copyBytes(from source: some Collection<UInt8>) {
     let buffer = Base(rebasing: self)
     buffer.copyBytes(from: source)
   }

stdlib/public/core/UnsafeRawBufferPointer.swift.gyb

@@ -534,16 +534,15 @@ extension Unsafe${Mutable}RawBufferPointer {
   /// - Parameter source: A collection of `UInt8` elements. `source.count` must
   ///   be less than or equal to this buffer's `count`.
   @inlinable
-  public func copyBytes<C: Collection>(from source: C
-  ) where C.Element == UInt8 {
+  public func copyBytes(from source: some Collection<UInt8>) {
     _debugPrecondition(source.count <= self.count,
       "${Self}.copyBytes source has too many elements")
     guard let position = _position else {
       return
     }
 
     if source.withContiguousStorageIfAvailable({
-      (buffer: UnsafeBufferPointer<C.Element>) -> Void in
+      (buffer: UnsafeBufferPointer<UInt8>) -> Void in
       if let base = buffer.baseAddress {
         position.copyMemory(from: base, byteCount: buffer.count)
       }