Make signrawtransaction* give an error when amount is needed but missing

Summary:

• Error on missing amount in signrawtransaction*

Signatures using segregated witness commit to the amount being spent,
so that value must be passed into signrawtransactionwithkey and
signrawtransactionwithwallet. This ensures an error is issued if that
doesn't happen, rather than just assuming the value is 0 and producing
a signature that is almost certainly invalid.

• [tests] Check signrawtransaction* errors on missing prevtx info

Backport of Core PR13547

Test Plan:

ninja all check-all

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D8082