Add aae_fold erase_keys

[pjaclark]

Docs are missing for this aae_fold. Should be added.

Usage is same as reap_tombs: Bucket, KeyRange, SegmentFilter, ModifiedRange, DeleteMethod

E.g. to delete all keys in bucket "bucketname" before 2023-05-01, call:

riak_client:aae_fold({
    erase_keys, 
    <<bucketname>>, 
    all, 
    all,
    {date,{{1970,1,1},{0,1,0}},{{2023,5,1},{0,0,0}}},
    local
    }, Client).

[pjaclark]

Done.