Report all errors encountered when trying to use mirrors
Report all errors encountered when trying to use mirrors

Don't change the error format when no mirrors are involved, but record
all errors when they are.

An example error:
(First tried mirrors: [docker.io/library/busybox:thisdoesnotexist: Error reading manifest thisdoesnotexist in docker.io/library/busybox: manifest unknown: manifest unknown]): does-not-exist-primary.example.com/library/busybox:thisdoesnotexist: error pinging docker registry does-not-exist-primary.example.com: Get https://does-not-exist-primary.example.com/v2/: dial tcp: lookup does-not-exist-primary.example.com on 192.168.64.1:53: no such host

This could obviously be improved with various user-focused heuristics
(e.g. prefer mirror TLS/authentication errors to primary DNS not found),
or by dropping unnecessary context in common cases of the individual errors,
but we can tinker with that later.

Signed-off-by: Miloslav Trmač <9c008e38982a5397deb855345fb164f0558459ae@redhat.com>

containers/image,containers/image