Check ports in a more cross-platform way.

[Karlinator]

related to #2020

We were using ports.blame() to check for port usage for the pretty error messages, but this silently fails on any system which does not have lsof. This PR instead uses ports.check(), which tries to listen to a port, as a more robust way to check if the port is in use. It still uses ports.blame() to find the process id using the port if possible.

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Latest commit: 1a56dba

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[Rich-Harris]

thank you!