scripts: update copyright_header script to include additional files

Summary:
Includes .sh and .bash-completion files in the script as well

This is a backport of core#17052

Depends on D9812

Test Plan: ./contrib/devtools/copyright_header.py report .

Reviewers: #bitcoin_abc, Fabien

Reviewed By: #bitcoin_abc, Fabien

Differential Revision: https://reviews.bitcoinabc.org/D9813