Relax coding standards for test files

[srtfisher]

Instead of ignoring test files and allowing code to be written in any format (https://github.com/alleyinteractive/create-wordpress-project/blob/develop/.phpcs.xml#L30) we should relax the standards for tests but still allow them to be reviewed by PHPCS. The suggestion is to adjust the standards to ensure that tests follow the WordPress coding style but aren't subject to the highest standards. This would mean relaxing the more dangerous sniffs such as direct database queries, meta queries, etc.

Acceptance Criteria

1. Tests can be included in PHPCS configurations and will not be excluded by create-wordpress-project/create-wordpress-plugin.
2. Tests won't be subject to many sniffs that don't apply to unit tests (direct database calls, meta queries, etc.).
3. Tests are written in this repository to enforce this.

[kevinfodness]

@srtfisher How is this coming along? How can we help?