Retry writing delta after concurrent modification exceptions

[istreeter]

Under most circumstances, Delta seamlessly handles any write conflicts caused by multiple instances of this loader.

However, there is one situation when Delta does not handle the conflict, and we get a DeltaConcurrentModificationException. This happens when another loader alters the table to add new columns. For example, when tracking a new schema for the first time.

Currently, the loader crashes and exits when this happens. Instead, when we get this exception we need to explicitly retry committing the files.