feat(shields): add physical layouts and update keymap for Jiran

Add physical layouts and update the keymap for Ladniy's Jiran.
Layouts are added for all three possible transforms:
- Full (with additional pinky key and number row)
- Jian (with additional pinky key), re-uses Jian layout
- 6 column (Corne), re-uses Jian layout

Keymap update includes &studio_unlock.

app/boards/shields/jiran/layouts/6column.dtsi

@@ -0,0 +1,20 @@
+#include <layouts/kgoh/jian/6column.dtsi>
+#include <physical_layouts.dtsi>
+
+#include "position_map.dtsi"
+
+&layouts_kgoh_jian_position_map {
+    status = "disabled";
+};
+
+&layouts_ladniy_jiran_position_map {
+    ladniy_jiran_6col_posmap: six {
+        physical-layout = <&kgoh_jian_6col_layout>;
+        positions
+            = <   42 43 44 45 46 47       48 49 50 51 52 53   >
+            , <54  0  1  2  3  4  5        6  7  8  9 10 11 55>
+            , <   12 13 14 15 16 17       18 19 20 21 22 23   >
+            , <   24 25 26 27 28 29       30 31 32 33 34 35   >
+            , <               36 37 38 39 40 41               >;
+    };
+};