When loading a template url from a custom plugin directory, prefix the relative directory #14717

In https://github.com/matomo-org/matomo/pull/14051 we started supporting multiple plugin paths.

There we already rewrite the path to the JS and CSS assets and load them from a different path. But it looks for some reason that a directive templateUrl is not loaded correctly when the plugin is located in a different path. It's still trying to load the template file eg from $matomoUrl/matomo/plugins/PluginName/angularjs/widgetname/widgetname.html when instead it should be maybe loaded from $matomoUrl/matomo/../extensions/PluginName/angularjs/widgetname/widgetname.html