Draft: limit ah search depth to 3000 rows

The limit on ah_rocksdb is 2000 and then it throws an exception with the next sequence
However, this implementation doesn't throw any exceptions and is only for postgrest hence MR is marked Draft
Only searches last 3000 rows for account history

I'm not so good at SQL or python to pull off the full implementation but this is good enough for me so I put the MR up