delta-find: rename `delta-reuse-policy` to `pulled-delta-reuse-policy` This make it clearer which type of delta we are talking about.

config-item: declare undeclared path suboption This should prevent issue like the previous commit.

delta-find: declare the "paths..*:delta-reuse-policy option While looking into renaming the option I realized it was not declared.

delta-find: adjust the default candidate group chunk size We move from 10 to 20 as the default as some usage in the wild saw a small degradation in storage quality when using `10`.