[LINTER] Move phpcs ruleset to a test/lint/phpcs directory
Having the ruleset file located near the arcanist sources is not ideal.
Moving it to its own directory under test/lint/phpcs makes more sense.
Depends on D3287
arc lint --everything
Reviewers: #bitcoin_abc, deadalnix
Reviewed By: #bitcoin_abc, deadalnix
Differential Revision: https://reviews.bitcoinabc.org/D3288