* Fixed issues with timeout in msgraph
Fixed a place where the cancellation token was not applied.
Fixed a problem with msgraph not sending correct DNS information.
Fixed a problem with msgraph downloading the entire file before streaming it, bypassing throttle and tripping the timeout.
Added `ITimeoutExemptBackend` to selectively disable timeouts for backends that do not support it.
Updated the backendmanager to support `ITimeoutExemptBackend`.
Updated the backendmanager to abort as soon as a timeout happens.
* Updated BackendTester to use the `TimeoutObservingStream` and support the `--read-write-timeout` setting.
Updated backend tester code to use `var`
* Fixed a bug reading the `read-write-timeout`
* Updated to using constants with names instead of `-1`.
