[mod] yahoo: fetch engine traits (data_type: traits_v1)

Implements a fetch_traits function for the Yahoo engine.

.. note::

   Includes migration of the request methode from 'supported_languages' to
   'traits' (EngineTraits) object!

Signed-off-by: Markus Heiser <markus.heiser@darmarit.de>

searx/data/engine_traits.json

@@ -6234,43 +6234,43 @@
     }
   },
   "yahoo": {
-    "all_locale": null,
-    "data_type": "supported_languages",
-    "languages": {},
+    "all_locale": "any",
+    "data_type": "traits_v1",
+    "languages": {
+      "ar": "ar",
+      "bg": "bg",
+      "cs": "cs",
+      "da": "da",
+      "de": "de",
+      "el": "el",
+      "en": "en",
+      "es": "es",
+      "et": "et",
+      "fi": "fi",
+      "fr": "fr",
+      "he": "he",
+      "hr": "hr",
+      "hu": "hu",
+      "it": "it",
+      "ja": "ja",
+      "ko": "ko",
+      "lt": "lt",
+      "lv": "lv",
+      "nl": "nl",
+      "no": "no",
+      "pl": "pl",
+      "pt": "pt",
+      "ro": "ro",
+      "ru": "ru",
+      "sk": "sk",
+      "sl": "sl",
+      "sv": "sv",
+      "th": "th",
+      "tr": "tr",
+      "zh_Hans": "zh_chs",
+      "zh_Hant": "zh_cht"
+    },
     "regions": {},
-    "supported_languages": [
-      "ar",
-      "bg",
-      "cs",
-      "da",
-      "de",
-      "el",
-      "en",
-      "es",
-      "et",
-      "fi",
-      "fr",
-      "he",
-      "hr",
-      "hu",
-      "it",
-      "ja",
-      "ko",
-      "lt",
-      "lv",
-      "nl",
-      "no",
-      "pl",
-      "pt",
-      "ro",
-      "ru",
-      "sk",
-      "sl",
-      "sv",
-      "th",
-      "tr",
-      "zh_chs",
-      "zh_cht"
-    ]
+    "supported_languages": {}
   }
 }