faebd2ef40 doc: Move wallet lock annotations to header (MarcoFalke)
Pull request description:
We put the annotations in a central place (the header) as opposed to spreading them over the cpp files, where they easily get outdated.
https://github.com/bitcoin/bitcoin/pull/15530/commits/faebd2ef40bf6c9209110ad4e229e5a207b9c9da
Backport of Core PR15530