Make ai::description's text field a t_string, and initialize it from one

Fixes bug #22092, which was caused by taking the translated form of a
WML attribute as a STL string only once.

changelog

@@ -40,6 +40,9 @@ Version 1.11.15+dev:
    * Added a button to copy the in-game Chat Log dialog contents to clipboard.
    * Fixed dependency check on MP mod locked to scenario on create game load
      checking against the first scenario instead of the last played scenario.
+   * Fixed AI engine names in the MP game setup screen being translated to the
+     language selected when Wesnoth was started rather than the current
+     language (bug #22092).
  * WML engine:
    * Fixed a regression in 1.11.14 causing WML parser/preprocessor errors to
      not interrupt the game load sequence or display an error message in-game,

src/ai/configuration.cpp

@@ -112,7 +112,7 @@ void configuration::init(const config &game_config)
 
 		description desc;
 		desc.id=id;
-		desc.text = ai_configuration["description"].str();
+		desc.text = ai_configuration["description"].t_str();
 		desc.cfg=ai_configuration;
 
 		ai_configurations_.insert(std::make_pair(id,desc));
@@ -137,7 +137,7 @@ void extract_ai_configurations(std::map<std::string, description> &storage, cons
 
 		description desc;
 		desc.id=id;
-		desc.text = ai_configuration["description"].str();
+		desc.text = ai_configuration["description"].t_str();
 		desc.cfg=ai_configuration;
 
 		storage.insert(std::make_pair(id,desc));

src/ai/configuration.hpp

@@ -51,7 +51,7 @@ struct description {
 	{
 	}
 
-	std::string text;
+	t_string text;
 	std::string id;
 	config cfg;
 };