[tests] remove txdb.h dependency from test_bitcoin.h
txdb.h is the one unnecessary dependency in test_bitcoin.h. It brings in
some heavy dependencies via chain.h and coins.h that result in unnecessary
recompilation work when various headers are changed.
Unfortunately numerous tests were relying on hidden indirect imports via
test_bitcoin.h -> txdb.h -> ??, so these tests needed the correct headers
to be added in.
Test Plan: compile
Reviewers: #bitcoin_abc, deadalnix, Fabien, jasonbcox
Reviewed By: #bitcoin_abc, Fabien
Differential Revision: https://reviews.bitcoinabc.org/D2963