[CI] Rename build.sh to build_autotools.sh

Summary:
This will allow for introducing a build_cmake.sh version.
Currently only convert the existing build-configuration to the new name
to make review easier.

Test Plan: Run the CI build configurations.

Reviewers: #bitcoin_abc, deadalnix, jasonbcox

Reviewed By: #bitcoin_abc, deadalnix, jasonbcox

Differential Revision: https://reviews.bitcoinabc.org/D4443