Remove -upgradewallet startup option

Summary:
Backport of Core PR15761 [6/6] : https://github.com/bitcoin/bitcoin/pull/15761/commits/0d32d661481f099af572e7a08a50e17bcc165c44

Depends on D7926

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D7927