[backport#17260 2/3] MOVEONLY: Move key handling code out of wallet to keyman file

Summary:
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.

https://github.com/bitcoin/bitcoin/pull/17260/commits/6702048f91089d7a565e5ca5f7c8dcd2ca405a85

Depends on D6998

Partial backport of Core PR17260

Test Plan:

ninja check check-functional

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D7006