[stdlib] incorporate proposal number in silgen name

Author: glessard

stdlib/public/core/UnsafeRawBufferPointer.swift.gyb

@@ -463,7 +463,7 @@ extension Unsafe${Mutable}RawBufferPointer {
   ///     with `type`.
   @inlinable
   @_alwaysEmitIntoClient
-  @_silgen_name("_swift_seNNNN_UnsafeMutableRawBufferPointer_storeBytes")
+  @_silgen_name("_swift_se0349_UnsafeMutableRawBufferPointer_storeBytes")
   public func storeBytes<T>(
     of value: T, toByteOffset offset: Int = 0, as type: T.Type
   ) {