fix: Memory leaks in SimpleWebTransport

[liamcary]

Handle several edge cases where ArrayBuffers were taken from the buffer pool but potentially not returned. Also handle exceptions to prevent Connection.Dispose exiting before releasing sendQueue.

[James-Frowen]

Have you seen Thread.Interrupt throw? I dont think SecurityException should ever be thrown in unity/mono or with the way we use it, because we both create and interrupt the thread there should be no permission issue

[liamcary]

I haven't, but i added it to be safe in case its extremely rare, or happens on windows but not linux, etc. Theoretically, security permission exceptions would have thrown earlier, when starting the thread. It's critical that Dispose continues executing, so i think its a good policy to handle every possible exception, even if it just serves as a reminder to people editing Dispose() in future. For these changes I just went to the docs for each method and added exception handling for methods that have any documented exceptions, and removed exception handling for those that don't.

[liamcary]

Copied from the websockets channel on discord, in case there was doubt that these changes were helping:

"I added some temporary logging to my fork to de-maybe-ify some of these changes. Changes in the SendLoop.Dispose() finally block and WebsocketServer.Send() are frequently being triggered, but not for every connection. From the first 14 closed connections, 4 connections were affected and 6 buffers were released that previously would have leaked."