Rename activity_level namespace to display

This namespace is presently only used as a wrapper to make
`activity_level_str` accessible to the crafting GUI, per CleverRaven#49026.

I intend to move several other descriptive functions defined in
`panels.h|cpp` into this namespace, making it a more general-purpose
collection of descriptive text and color translation methods. Hence, the
namespace is here renamed to `display`.

src/crafting_gui.cpp

@@ -232,7 +232,7 @@ static std::vector<std::string> recipe_info(
                           recp.batch_savings_string() );
 
     oss << string_format( _( "Activity level: <color_cyan>%s</color>\n" ),
-                          activity_level::activity_level_str( recp.exertion_level() ) );
+                          display::activity_level_str( recp.exertion_level() ) );
 
     const int makes = recp.makes_amount();
     if( makes > 1 ) {

src/panels.cpp

@@ -1012,7 +1012,7 @@ static std::pair<translation, nc_color> weariness_description( size_t weariness
     return weary_descriptions[weariness];
 }
 
-std::string activity_level::activity_level_str( float level )
+std::string display::activity_level_str( float level )
 {
     static const std::array<translation, 6> activity_descriptions { {
             to_translation( "activity description", "None" ),
@@ -1075,7 +1075,7 @@ static void draw_stats( avatar &u, const catacurses::window &w )
     mvwprintz( w, point( wlabel_len + 1, 1 ), weary.second, weary.first.translated() );
     mvwprintz( w, point( act_start, 1 ), c_light_gray, _( activity_label ) );
     mvwprintz( w, point( act_start + alabel_len + 1, 1 ), act_color,
-               activity_level::activity_level_str( activity ) );
+               display::activity_level_str( activity ) );
 
     wnoutrefresh( w );
 }
@@ -1393,7 +1393,7 @@ static void draw_stat_narrow( avatar &u, const catacurses::window &w )
     mvwprintz( w, point( wlabel_len + 2, 3 ), weary.second, weary.first.translated() );
     mvwprintz( w, point( act_start, 3 ), c_light_gray, _( activity_label ) );
     mvwprintz( w, point( act_start + alabel_len + 1, 3 ), act_color,
-               activity_level::activity_level_str( activity ) );
+               display::activity_level_str( activity ) );
 
     wnoutrefresh( w );
 }
@@ -1444,7 +1444,7 @@ static void draw_stat_wide( avatar &u, const catacurses::window &w )
     mvwprintz( w, point( wlabel_len + 2, 2 ), weary.second, weary.first.translated() );
     mvwprintz( w, point( act_start, 2 ), c_light_gray, _( activity_label ) );
     mvwprintz( w, point( act_start + alabel_len + 1, 2 ), act_color,
-               activity_level::activity_level_str( activity ) );
+               display::activity_level_str( activity ) );
 
     wnoutrefresh( w );
 }
@@ -2242,7 +2242,7 @@ static void draw_weariness_classic( const avatar &u, const catacurses::window &w
     mvwprintz( w, point( wlabel_len + 1, 0 ), weary.second, weary.first.translated() );
     mvwprintz( w, point( act_start, 0 ), c_light_gray, _( activity_label ) );
     mvwprintz( w, point( act_start + alabel_len + 1, 0 ), act_color,
-               activity_level::activity_level_str( activity ) );
+               display::activity_level_str( activity ) );
 
     std::pair<int, int> bar = u.weariness_transition_progress();
     std::pair<std::string, nc_color> weary_bar = get_hp_bar( bar.first, bar.second );

src/panels.h

@@ -16,10 +16,13 @@ class JsonOut;
 class avatar;
 struct point;
 
-namespace activity_level
+// The display namespace contains UI string output and colorization functions
+// Some return plain strings or translations, some return a (string, color) pair,
+// and some return a string with colorization tags embedded.
+namespace display
 {
 std::string activity_level_str( float level );
-} // namespace activity_level
+} // namespace display
 
 namespace catacurses
 {