implement SE 184: add allocation methods to Unsafe buffer pointers, drop all parameters from deallocation, adjust namings, and add repeated-value assignment methods

stdlib/private/StdlibCollectionUnittest/CheckSequenceInstance.swift.gyb

@@ -95,7 +95,7 @@ public func checkSequence<
       "_copyContents failed to use entire buffer")
     expectEqualSequence(expected, buf, ${trace}, sameValue: sameValue)
     ptr.deinitialize(count: count)
-    ptr.deallocate(capacity: count)
+    ptr.deallocate()
   }
 
   // Test `_copyToContiguousArray()` if we can do so
@@ -124,4 +124,3 @@ public func checkSequence<
 }
 
 % end
-