Move refactor/rename custom events into map- namespace

Corresponding [polyfill](https://github.com/Maps4HTML/Web-Map-Custom-Element/issues/868), [spec](https://github.com/Maps4HTML/MapML/issues/253),  [extension](https://github.com/Maps4HTML/mapml-extension/issues/64), and [experiments](https://github.com/Maps4HTML/experiments/issues/121) issues