Merge #11351: Refactor: Modernize disallowed copy constructors/assignment

Summary:
2a07f878a Refactor: Modernize disallowed copy constructors/assignment (Dan Raviv)

Pull request description:

Use C++11's better capability of expressing an interface of a non-copyable class by publicly deleting its copy ctor and assignment operator instead of just declaring them private.

Tree-SHA512: 878f446be5a136bb2a90643aaeaca62948b575e6ef71ccc5b4b8f373e66f36ced00665128f36504e0ccfee639863d969329c4276154ef9f2a9de9137f0801e01

Backport of Core PR11351
https://github.com/bitcoin/bitcoin/pull/11351

Test Plan:
make check
test_runner.py

Reviewers: jasonbcox, deadalnix, Fabien, O1 Bitcoin ABC, #bitcoin_abc, markblundeberg

Reviewed By: O1 Bitcoin ABC, #bitcoin_abc, markblundeberg

Subscribers: markblundeberg

Differential Revision: https://reviews.bitcoinabc.org/D2983