Make sure we read the command line inputs using utf-8 decoding in python

Summary:
Backport of core PR14128.

Extend our python encodings linter to cover check_output.

Test Plan:

arc lint --everything

Remove one of the encodings arguments and run arc lint. Check the
linter returns an error.

Run the scripts.

Reviewers: #bitcoin_abc, deadalnix

Reviewed By: #bitcoin_abc, deadalnix

Subscribers: deadalnix

Differential Revision: https://reviews.bitcoinabc.org/D5957