[backport#17260 2/3] MOVEONLY: Move key handling code out of wallet to keyman file
Start moving wallet and ismine code to scriptpubkeyman.h, scriptpubkeyman.cpp
The easiest way to review this commit is to run:
git log -p -n1 --color-moved=dimmed_zebra
And check that everything is a move (other than includes and copyrights comments).
This commit is move-only and doesn't change code or affect behavior.
Depends on D6998
Partial backport of Core PR17260
ninja check check-functional
Reviewers: #bitcoin_abc, deadalnix
Reviewed By: #bitcoin_abc, deadalnix
Differential Revision: https://reviews.bitcoinabc.org/D7006