Merge #12327: [gui] Defer coin control instancing

Summary:
6558f8acc [gui] Defer coin control instancing (João Barbosa)

Pull request description:

Defer the GUI coin control instancing so that argument processing
is taken into account for the default coin control values.

Fixes #12312

Tree-SHA512: ecda28b94f4709319e9484b01afe763c7c3569097d2afb89db79da8a195c46d20ea77166df7edce0c8ab77627b295def01c072148714503436d27675d5e75d99

Backport of Core PR 12327
https://github.com/bitcoin/bitcoin/pull/12327/files
Completes T556

Test Plan:
make check
test_runner.py

Reviewers: deadalnix, Fabien, #bitcoin_abc

Reviewed By: Fabien, #bitcoin_abc

Subscribers: teamcity, schancel

Differential Revision: https://reviews.bitcoinabc.org/D2693