Add a deprecation notice for the autotools build system

Summary:
This add a mandatory option to run the configure script. The configure
stage will fail if the --enable-deprecated-build-system is not set,
and an error message instructs the user of the deprecation.

Depends on D5823.

Test Plan:

./configure

Check it fails early with the error message

./configure --enable-deprecated-build-system
make

Check the build succeeds as usual.

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D5824