[backport#15288] Remove use of IsRBFOptIn in wallet code

Summary:
bdc6628683197945326cbdfea3f53ec0b7d1949f This commit does not change behavior. (Russell Yanofsky)

Depends on D5816

This is a partial backport of Core PR15288, mostly RBF related which I left out, except for one header that looks like will be needed in the next commits

Test Plan:

ninja check

Reviewers: #bitcoin_abc, jasonbcox, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: deadalnix, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D5819