feat: Handle and retry CAS upload failures

[jiparis]

If there is a network problem, for instance we might get

ERR[0m [1madding material: crafting material: error crafting material: upload and craft error: uploading material: sending the finished upload message EOF[0m

It doesn't seem to be retrying, and the message is confusing and not providing a real cause nor solution. If it's a network problem, it should say it.

[javirln]

Controlplane is retrying when trying to store the attestation to the CAS:

chainloop/app/controlplane/internal/service/attestation.go

Line 253 in 77e39b1

b := backoff.NewExponentialBackOff()

[migmartri]

Did we determine the root cause of the error we originally got? Was it transient?