build: add -fcf-protection=full to hardening options and test for control flow instrumentation

Summary:

build: add -fcf-protection=full to hardening options

Enables code instrumentation of control-flow transfers. Available in
GCC 8 and Clang 7.

This option is now on by default in Ubuntu GCC as of 19.10.

This is a backport of core#18921, core#21889, core#23535 and core#23839
https://github.com/bitcoin/bitcoin/pull/18921/commits/076183b36b76a11438463883ff916f17aef9e001

Test Plan: guix build and gitian builds

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Subscribers: Fabien

Differential Revision: https://reviews.bitcoinabc.org/D14008