Merge L and Z button action (#120)

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## Description
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Merge the L and Z action to be the "same" button press, depending on how
the joypad is gripped.

## Motivation and Context
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issue here -->
Simplifies the menu controls.

https://github.com/Polprzewodnikowy/N64FlashcartMenu/pull/119#issuecomment-2218853256

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## Types of changes
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- [ ] Bug fix (fixes an issue)
- [ ] Breaking change (breaking change)
- [ ] Config and build (change in the configuration and build system,
has no impact on code or features)

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- [ ] All new and existing tests passed.

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src/menu/actions.c

@@ -21,8 +21,7 @@ static void actions_clear (menu_t *menu) {
     menu->actions.back = false;
     menu->actions.options = false;
     menu->actions.settings = false;
-    menu->actions.l_context = false;
-    menu->actions.z_context = false;
+    menu->actions.lz_context = false;
 }
 
 static void actions_update_direction (menu_t *menu) {
@@ -93,10 +92,8 @@ static void actions_update_buttons (menu_t *menu) {
         menu->actions.options = true;
     } else if (pressed.start) {
         menu->actions.settings = true;
-    } else if (pressed.l) {
-        menu->actions.l_context = true;
-    }  else if (pressed.z) {
-        menu->actions.z_context = true;
+    } else if (pressed.l || pressed.z) {
+        menu->actions.lz_context = true;
     }
 }
 

src/menu/menu_state.h

@@ -85,8 +85,7 @@ typedef struct {
         bool back;
         bool options;
         bool settings;
-        bool l_context;
-        bool z_context;
+        bool lz_context;
     } actions;
 
     struct {