wallet: Add GetPrefixCursor to DatabaseBatch

In order to get records beginning with a prefix, we will need a cursor
specifically for that prefix. So add a GetPrefixCursor function and
DatabaseCursor classes for dealing with those prefixes.

Tested on each supported db engine.

1) Write two different key->value elements to db.
2) Create a new prefix cursor and walk-through every returned element,
   verifying that it gets parsed properly.
3) Try to move the cursor outside the filtered range: expect failure
   and flag complete=true.

Co-Authored-By: Ryan Ofsky <ryan@ofsky.org>
Co-Authored-By: furszy <matiasfurszyfer@protonmail.com>

0 files changed, 0 insertions, 0 deletions