Remove direct bitcoin calls from qt/coincontroldialog.cpp

Summary:
Partial backport of Core PR 10244
https://github.com/bitcoin/bitcoin/pull/10244/commits/827de038ab6fa58aa3d46151eb2f8dc6add7743e
Progress towards T417

Test Plan:
make check
bitcoin-qt # sanity checking: use coin control dialog to select inputs for generating a tx

Reviewers: #bitcoin_abc, deadalnix, Fabien

Reviewed By: #bitcoin_abc, Fabien

Tags: #bitcoin_abc

Differential Revision: https://reviews.bitcoinabc.org/D2884