Various test changes

[wrexbe]

Tests fall apart when you try to reuse instances, these changes make them fall apart less often, and also let me bypass the current testing pool, so I can setup/clean/pool them differently.
Contains:

• Duct tape
• • Ping handling ServerChannel being null so it doesn't blow up in the tests sometimes
• • UpdateAttachedEntity being better at dealing with garbage (although I think garbage still gets through sometimes)
• • Wrap _fromInstanceReader.ReadAsync(cancellationToken); in a try, catch. It just makes it more graceful if it cancels.
• Pooling fixes
• • Make DataDefinitions not static, they are not the same between different instances (ex: client vs server, or different settings)
• • Add DoConnect to the _taskManager, which makes stuff wait for DoConnect to finish, which makes it more reliable, instead of based on luck.
• Bypass Pooling
• • Made ServerIntegrationInstance, and ClientIntegrationInstance public, so I can avoid the built in pooling. (which is very unreliable right now)
• Ignore missing types, and ids when removing prototypes with a string
• • If I add prototypes to both the client/server, they may not all be added because of differences between types
• • So I need remove to ignore missing things to undo what add is doing.

Content side (should not be needed for this PR): space-wizards/space-station-14#8737