Improve exec loop handling for webassembly

Currently exec loop handling has issues with 'child loops', secondary MainWindows and local event loops.

More details on the Issue: Currently exec loop handling has issues with nested event loops, for example when displaying dialogs. It could also cause 100% cpu usage and application freezeing when used on a secondary thread.
Solution: Patches have been done to allow main threads to run using asyncify - Asyncify automatically transforms your compiled code into a form that can be paused and resumed, and handles pausing and resuming for you, so that it is asynchronous (hence the name “Asyncify”) even though you wrote it in a normal synchronous way. Event loop can be run on the secondary thread.
 In testing CPU load reduced from 100% to 2% in problematic cases.
This feature enables many other things such as sockets on a secondary thread