convert to withCreateProcess for async exception safety

This handles all createProcessSuccess callers, and aside from process
pools, the complete conversion of all process running to async exception
safety should be complete now.

Also, was able to remove from Utility.Process the old API that I now
know was not a good idea. And proof it was bad: The code size went *down*,
despite there being a fair bit of boilerplate for some future API to
reduce.

Utility/CopyFile.hs

@@ -57,11 +57,12 @@ copyCoW meta src dest
 		void $ tryIO $ removeFile dest
 		-- When CoW is not supported, cp will complain to stderr,
 		-- so have to discard its stderr.
-		ok <- catchBoolIO $ do
-			withQuietOutput createProcessSuccess $
-				proc "cp" $ toCommand $
-					params ++ [File src, File dest]
-			return True
+		ok <- catchBoolIO $ withNullHandle $ \nullh ->
+			let p = (proc "cp" $ toCommand $ params ++ [File src, File dest])
+				{ std_out = UseHandle nullh
+				, std_err = UseHandle nullh
+				}
+			in withCreateProcess p $ \_ _ _ -> checkSuccessProcess
 		-- When CoW is not supported, cp creates the destination
 		-- file but leaves it empty.
 		unless ok $