[BUG] Custom events do not report client_OS correctly about applicationinsights-js

[MSNev]

Yes, this is caused because the UserAgent is now frozen (the browser lies to us via the UA about which OS version it's running on).

And because this information is currently processed by the server it is only receiving the UA (it's not requesting the new Client hints) the best it can currently do is to identify this based on what is provided.

There are a couple of long term internal investigatings (on the client side) that we are planning which (might) help with this -- but I don't have any concrete dates on when the investigation will occur (this is to use the getHighEntrophyData() API (which is asynchronous (which will affect the initial page load), we have already updated the code to use the browser performance timings (rather than the JavaScript time) for reporting the initial page load (this was the first step), the next step is that due to the asynchronous nature of the getHighEntrophyData() call, to correctly "handle" the reporting we would have to delay the page view (even if you ask for it and call flush) -- this is not quite as straight forward as it sounds to do from a generic perspective.