Minor cleanup/refactor of some logic

[LahaLuhem]

I made some improvements:

1. Simplified hasInternetAccess logic
   • Split into two separate methods _hasInternetAccessStrict and _hasInternetAccessNonStrict
   • Removed complex completer logic and race conditions
   • Used Future.wait for strict mode and sequential checking for non-strict mode
2. Cleaned up _maybeEmitStatusUpdate
   • Moved early return to the top for better readability
   • Removed duplicate listener checks
   • Made the control flow more linear
3. Simplified _handleStatusChangeCancel
   • Removed unnecessary then callback for subscription cancellation
   • Made the method more straightforward
4. Improved _checkReachabilityFor: use null assertion operator for cleaner code
5. Better error handling in _hasInternetAccessNonStrict: added try-catch to handle individual endpoint failures gracefully

I did this in the context to be better be able to support the new feature request in #71

[OutdatedGuy]

Lots of unnecessary formatting changes. Please revert them first.

[LahaLuhem]

You have not defined any kind of formatting guidelines. The code is not even formatted, as these kinds of changes would appear if you'd just run dart format ..
Nevertheless I will try to undo those kinds of changes. But please consider adding some more rules to the analysis_options.yml

[LahaLuhem]

@OutdatedGuy I have reverted most of the formatting