k8up-restic: pass exclude/file-from flags to restic from PVC annotations

[webconn]

Summary

This PR partially solves #317 by adding PVC annotations to pass some flags to restic in k8up wrapper, such as:

• --exclude of all kinds
• --files-from of all kinds
• --one-file-system (not sure if it is actually necessary but kept it in case of complex mounts in backup job container)

It also properly splits backups between jobs if PVCs with different args annotations are involved :)

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[Kidswiss]

Thanks for the contribution!

I've triggered the E2E tests, if they pass, it should be good to merge!

[webconn]

I've merged conflicting upstream changes, could you please run checks again? It worked OK last time