Fixes #1212. Some async operations accept a cancellation token and pass it through to the IO operations they perform. If the IO operations are cancelled then we may end up in one of the following states:

• The request was not fully written to the stream
  • If we perform another operation on the stream, the request will not be interpreted correctly by the database
• We have a complete response waiting to be read from the underlying stream
  • If we perform another operation on the stream, the responses will be out of alignment
• The response was not fully read from the stream
  • If we perform another operation on the stream, the response will not be interpreted correctly by the client

This can be demonstrated by opening a connection, beginning a transaction, and cancelling the request immediately, which has been added as a test case.

I couldn't see an easy way to ignore frames that were interrupted or don't align to the current request/response, so when an IO operation is cancelled I have opted to treat it the same as an IO exception. The connection is marked as broken and removed from the connection pool.

TODO: I haven't checked this for compatibility with all the supported build configurations and Firebird versions. I'm hoping this is covered by the build pipeline, otherwise I will need some guidance on this.

AI usage

As per the contributor guidelines, this code was implemented by Cursor. I have reviewed it to make sure I fully understand the problem and approve of the solution that was implemented.