batch.readFile will now await doReadRow

[wilwade]

Problem

Wanted to be able to perform async actions inside of doReadRow #179386996

Solution

Expanded the signature to allow for void or Promise and await'd the callback

Double Checks:

• [x] Did you update the changelog?
• [x] Any new modules need to be exported?
• [x] Are new methods in the right module?
• [x] Are new methods/modules in core or not (i.e. porcelain or plumbing)?
• [x] Do you have good documentation on exported methods?