Utils: Move process arguments class out of QtcProcess

The main QtcProcess interface is nowadays a CommandLine, with no
explicit references left to QtcProcess::Arguments and related static
helper functions, so it only clutters the QtcProcess class interface

So move these items out of QtcProcess, later potentially to a separate
file pair.

Change-Id: I45c300b656f5b30e2e2717232c855fdd97c2d1d7
Reviewed-by: Christian Stenger <christian.stenger@qt.io>

src/libs/ssh/sftpsession.cpp

@@ -102,7 +102,7 @@ struct SftpSession::SftpSessionPrivate
 
         // The second newline forces the prompt to appear after the command has finished.
         sftpProc.write(commandString(activeCommand.type) + ' '
-                       + QtcProcess::Arguments::createUnixArgs(activeCommand.paths)
+                       + ProcessArgs::createUnixArgs(activeCommand.paths)
                        .toString().toLocal8Bit() + "\n\n");
     }
 };