[wallet] abort when attempting to fund a transaction above maxtxfee

Summary:
FundTransaction calls GetMinimumFee which, when the fee rate is absurdly high, quietly reduced the fee to -maxtxfee. Becaue an absurdly high fee rate is usually the result of a fat finger, aborting seems safer behavior.

This is a backport of Core PR16257

Depends on D6267

Test Plan:

ninja all check-all

Also run the test suite on the no wallet build

Reviewers: #bitcoin_abc, jasonbcox

Reviewed By: #bitcoin_abc, jasonbcox

Subscribers: jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D6268