Redesigned LLM model selection in AI Assistant chat UI (now it's possible to search by filtering its name).

Redesigned UIDropDownList to inherit from UIDropDown which is a base class to handle different types of drop-downs. Added UIDropDownModelList which is the same as UIDropDownList but uses a UIListView by default so it's a model/view based DropDown.
Fix crash when changing states of the buttons in the build panel.
Increased the default animations speed.

.ecode/project_build.json

@@ -369,6 +369,12 @@
         "command": "${project_root}/bin/eepp-ui-markdownview-debug",
         "name": "eepp-ui-markdownview-debug",
         "working_dir": "${project_root}/bin"
+      },
+      {
+        "args": "",
+        "command": "${project_root}/bin/eepp-ui-dropdownmodellist-debug",
+        "name": "eepp-ui-dropdownmodellist-debug",
+        "working_dir": "${project_root}/bin"
       }
     ],
     "var": {