Fix shop reroll button's horizontal movement (#316) (#425)

* Add optional exit indexes to selection grid rows & fix shop reroll button movement (#316)

- Added has_exit_idx and exit_idx to SelGridRowAttributes to simulate subgrid-like behavior that was desired in shop reroll button
- Add logic to use exit index if given inside selection_grid_move_selection_horz()
- Add joker focus logic to shop_reroll_row_on_selection_changed()

* clang-format fix

* clang format fix #2

errors due to version mismatch in local fixed (i hope)

* important fix: check x instead of y for next_roudn_btn_sel_x

was checking y against an X value

* changed commenting

* selection_grid.h clang-format fix

* changed commenting again

trying to make docs understandable

* set shop selection rows explicit

Co-authored-by: Rickey <ric@rf3.xyz>

* syntax fix

* clang format fix onceagain

* guard clause when moving down from jokers

---------

Co-authored-by: Rickey <ric@rf3.xyz>

include/selection_grid.h

@@ -82,6 +82,17 @@ typedef struct
      * @brief Whether to wrap selection when it passes the end of the row.
      */
     bool wrap;
+
+    /**
+     * @brief Whether this row have a horizontal exit index (a row to process horizontal inputs
+     * from).
+     */
+    bool has_h_exit_idx;
+
+    /**
+     * @brief The index of the row to exit from when a horizontal input is received.
+     */
+    u8 h_exit_idx;
 } SelGridRowAttributes;
 
 /**