Cleanup (UI): Add/use type for operator context enum

Adds a `wmOperatorCallContext` typedef for the existing `WM_OP_XXX`
operator context enum. This adds type safety, allows the compiler to
produce better warnings and helps understanding what a variable is for.

Differential Revision: https://developer.blender.org/D13113

Reviewed by: Campbell Barton

source/blender/editors/interface/interface_templates.c

@@ -1741,7 +1741,7 @@ static void template_search_add_button_name(uiBlock *block,
 
 static void template_search_add_button_operator(uiBlock *block,
                                                 const char *const operator_name,
-                                                const int opcontext,
+                                                const wmOperatorCallContext opcontext,
                                                 const int icon,
                                                 const bool editable)
 {