Optimize validation tests

[paulbalandan]

Description

• Add type declarations
• Remove unnecessary multilines, whitespaces, comments
• Use generators in data providers (for efficient memory consumption)
• Move database related rules testing into own file (to reduce DB load on non-DB tests)
• Group several related tests using a data provider (for scalability of testing)

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[MGatner]

All good rubrics and the tests are passing so I won't go through it all. I do like @kenjis suggestions. Mention me if you need anything else.