Add performance related rules and no unlimited queries sniff

[pabamato]

Description of the Change

• Add missing DB and performance related sniffs
• Add custom sniff to flag queries using -1 (unlimited) for posts_per_page

Closes # #40

How to test the Change

Changelog Entry

Added - PostsPerPageNoUnlimited sniff. Detect usage of -1 on posts_per_page
This feature has been removed from WordPress and VIP-go CS: WordPress/WordPress-Coding-Standards#1531 (review)

Added - Import the following rules from WordPress CS:
WordPress.DB.PreparedSQL, WordPress.DB.DirectDatabaseQuery, WordPress.DB.SlowDBQuery

Credits

Checklist:

• [ x] I agree to follow this project's Code of Conduct.
• I have updated the documentation accordingly.
• I have added tests to cover my change.
• All new and existing tests pass.