Plot on all layers prep work.

We only need one bottom to top layer sequence definition.

Plot a sequence of layer IDs (LSEQ) in the order of the sequence.

Add helper method to layer set (LSET) to create a sequence of layer IDs
using another sequence for ordering.

common/lset.cpp

@@ -2,7 +2,7 @@
  * This program source code file is part of KiCad, a free EDA CAD application.
  *
  * Copyright (C) 2014 SoftPLC Corporation, Dick Hollenbeck <[email protected]>
- * Copyright (C) 2014-2020 KiCad Developers, see AUTHORS.txt for contributors.
+ * Copyright (C) 2014-2022 KiCad Developers, see AUTHORS.txt for contributors.
  *
  * This program is free software; you can redistribute it and/or
  * modify it under the terms of the GNU General Public License
@@ -30,7 +30,7 @@
 
 #include <core/arraydim.h>
 #include <math/util.h>                        // for Clamp
-#include <layer_ids.h>  // for LSET, PCB_LAYER_ID, LSEQ
+#include <layer_ids.h>                        // for LSET, PCB_LAYER_ID, LSEQ
 #include <macros.h>                           // for arrayDim
 #include <wx/debug.h>                         // for wxASSERT, wxASSERT_MSG
 #include <wx/string.h>
@@ -442,6 +442,20 @@ LSEQ LSET::Seq( const PCB_LAYER_ID* aWishListSequence, unsigned aCount ) const
 }
 
 
+LSEQ LSET::Seq( const LSEQ& aSequence ) const
+{
+    LSEQ ret;
+
+    for( LSEQ seq = aSequence; seq; ++seq )
+    {
+        if( test( *seq ) )
+            ret.push_back( *seq );
+    }
+
+    return ret;
+}
+
+
 LSEQ LSET::Seq() const
 {
     LSEQ    ret;