Pcbnew: ignore start values in "first available" grid numbering

The using the "first available" numbering option, force an
artifical linear numbering scheme starting at '1'.

Start the pad name provider at the 0'th pad index.

Also adds a few related tests and adjusts tests affected by
this change to reflect that the offset still applies.

This can be expanded in future to be more general by skipping
pad (which would allow a custom start and numbering scheme
while still avoiding duplication), but for now,
this does what the UI says and avoids string changes in 5.1rc.

Fixes: lp:1814918
* https://bugs.launchpad.net/kicad/+bug/1814918

Fixes: lp:1814917
* https://bugs.launchpad.net/kicad/+bug/1814917

qa/common/test_array_options.cpp

@@ -397,6 +397,7 @@ struct GRID_ARRAY_NAMING_PARAMS
     std::string                     m_start_at_x;
     std::string                     m_start_at_y;
     bool                            m_2d_numbering;
+    bool                            m_h_then_v;
     int                             m_nx;
     int                             m_ny;
 };
@@ -420,20 +421,54 @@ static const std::vector<GRID_ARRAY_NAMING_CASE> grid_name_cases = {
             "1",
             "2",
             false,
+            false, // doesn't matter
             2,
             3,
         },
         { "1", "2", "3", "4", "5", "6" },
     },
+    {
+        // Tests a 2d grid
+        "2D grid A1",
+        {
+            ARRAY_OPTIONS::NUMBERING_TYPE_T::NUMBERING_ALPHA_FULL,
+            ARRAY_OPTIONS::NUMBERING_TYPE_T::NUMBERING_NUMERIC,
+            "A",
+            "1",
+            true,
+            true,
+            2,
+            3,
+        },
+        { "A1", "B1", "A2", "B2", "A3", "B3" },
+    },
+    {
+        // Tests a 2d grid
+        "2D grid 11",
+        {
+            ARRAY_OPTIONS::NUMBERING_TYPE_T::NUMBERING_NUMERIC,
+            ARRAY_OPTIONS::NUMBERING_TYPE_T::NUMBERING_NUMERIC,
+            "1",
+            "1",
+            true,
+            false,
+            2,
+            3,
+        },
+        // moving down the "long axis" first
+        // so the first coordinate has a range of 1-3, the second 1-2
+        { "11", "21", "31", "12", "22", "32" },
+    },
     {
         // Tests a 2d grid, with different types and offsets (and alphabet wrap)
-        "2D grid",
+        "2D grid offsets",
         {
             ARRAY_OPTIONS::NUMBERING_TYPE_T::NUMBERING_NUMERIC,
             ARRAY_OPTIONS::NUMBERING_TYPE_T::NUMBERING_ALPHA_FULL,
             "5",
             "Z",
             true,
+            true,
             2,
             3,
         },
@@ -457,6 +492,8 @@ BOOST_AUTO_TEST_CASE( GridNaming )
             grid_opts.m_nx = c.m_prms.m_nx;
             grid_opts.m_ny = c.m_prms.m_ny;
 
+            grid_opts.m_horizontalThenVertical = c.m_prms.m_h_then_v;
+
             ARRAY_OPTIONS::GetNumberingOffset(
                     c.m_prms.m_start_at_x, c.m_prms.m_pri_type, grid_opts.m_numberingOffsetX );
             ARRAY_OPTIONS::GetNumberingOffset(