[backport#15931 2/9] Add m_last_block_processed_height field in CWallet

Summary:
At BlockConnected/BlockDisconnected, we rely on height of block
itself to know current height of wallet

https://github.com/bitcoin/bitcoin/pull/15931/commits/5aacc3eff15b9b5bdc951f1e274f00d581f63bce

Depends on D7506

Partial backport of Core PR15931

Test Plan:

ninja check check-functional

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D7507