Move PSBT definitions and code to separate files
Summary:
Move non-wallet PSBT code to src/psbt.{h,cpp}, and PSBT wallet code to
src/wallet/psbtwallet.{h,cpp}. This commit contains only code movement
(and adjustments to includes and Makefile.am.)Partial backport of core PR14978:
https://github.com/bitcoin/bitcoin/pull/14978/commits/c6c3d42a7d6b525144fc7fc6653cd11139d2b34a
Depends on D5715.
Test Plan:
ninja check check-functional
Reviewers: #bitcoin_abc, deadalnix
Reviewed By: #bitcoin_abc, deadalnix
Differential Revision: https://reviews.bitcoinabc.org/D5718