Enhancement: Allow including or excluding extended file attributes
during restore.

# Describe the problem in the past tense, the new behavior in the present
# tense. Mention the affected commands, backends, operating systems, etc.
# If the problem description just says that a feature was missing, then
# only explain the new behavior.
# Focus on user-facing behavior, not the implementation.
# Use "Restic now ..." instead of "We have changed ...".
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Restic restore used to attempt to restore all extended file attributes.
Now two new command line flags are added to restore to control which
extended file attributes will be restored.

The new flags are `--exclude-xattr` and `--include-xattr`.

If the flags are not provided, restic will default to restoring
only `user` namespaced extended file attributes on Linux, and all
extended file attributes on other operating systems.

https://github.com/restic/restic/issues/5089
https://github.com/restic/restic/pull/5129