Refactor the php-error command to use the new endpoint for logs

[tiagonoronha]

New endpoint: https://my.pressable.com/documentation/api/v1#get-php-logs

Command: https://github.com/Automattic/team51-cli/blob/trunk/src/commands/pressable-site-php-errors.php

[ahegyes]

Linking #173 and noting that the API endpoints are unlikely to return the logs when WP_DEBUG is turned on, whereas the current method does support that. So this scenario must be investigated as well :)