libgit2: Improved logging

[pjbgf]

Debugging connection issues can be extremely difficult,
even more so at scale or when concurrent connections are
required to trigger specific issues.

The changes create an unique identifier for each
SubTransport instance, which allows for greater traceability
when going through all the steps throughout the transport
lifecicle.

Example of stdout output when grepping by a specific TransportID:

..."msg":"[ssh]: sshSmartSubtransport.Close()","server":"","TransportID":"64d598f7-62cd-4e23-b2ad-f4ec0350b254"...
..."msg":"[ssh]: sshSmartSubtransport.Close()","server":"source.developers.google.com:2022","TransportID":"64d598f7-62cd-4e23-b2ad-f4ec0350b254"...
..."msg":"[ssh] dial connection","server":"source.developers.google.com:2022","TransportID":"64d598f7-62cd-4e23-b2ad-f4ec0350b254"...
..."msg":"[ssh]: creating new ssh session","server":"source.developers.google.com:2022","TransportID":"64d598f7-62cd-4e23-b2ad-f4ec0350b254"...
..."msg":"[ssh]: run on remote","cmd":"git-upload-pack '/p/kubetestlocal/r/flux-testing'","server":"source.developers.google.com:2022","TransportID":"64d598f7-62cd-4e23-b2ad-f4ec0350b254"...
..."msg":"[ssh]: sshSmartSubtransport.Close()","server":"source.developers.google.com:2022","TransportID":"64d598f7-62cd-4e23-b2ad-f4ec0350b254"...
..."msg":"[ssh]: session.Close()","server":"source.developers.google.com:2022","TransportID":"64d598f7-62cd-4e23-b2ad-f4ec0350b254"...
..."msg":"[ssh] close client","server":"source.developers.google.com:2022","TransportID":"64d598f7-62cd-4e23-b2ad-f4ec0350b254"...
..."msg":"[ssh]: sshSmartSubtransport.Close()","server":"source.developers.google.com:2022","TransportID":"64d598f7-62cd-4e23-b2ad-f4ec0350b254"...
..."msg":"[ssh] close client","server":"source.developers.google.com:2022","TransportID":"64d598f7-62cd-4e23-b2ad-f4ec0350b254"...
..."msg":"[ssh]: sshSmartSubtransport.Close()","server":"source.developers.google.com:2022","TransportID":"64d598f7-62cd-4e23-b2ad-f4ec0350b254"...
..."msg":"[ssh] close client","server":"source.developers.google.com:2022","TransportID":"64d598f7-62cd-4e23-b2ad-f4ec0350b254"...

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⚠️ This PR will be rebased once #775 is merged

[darkowlzz]

Maybe we should use github.com/google/uuid instead? The whole package is specifically made for uuid and we already have it in our dependencies.

[darkowlzz]

Instead of adding a correlation ID here, we can make use of the perfect tool for it, context.WithValue(), and pass the ID in a context. I think it'd be in alignment with libraries like opentelemetry-go if we adopt them in the future.

[pjbgf]

Superseeded by #778