feat: rework "containing" selectors via addition of remaining attribute operators

[joelpop]

Description

Refactored name of "xContaining" attribute selector methods to "xContainingToken".

Added true "xContaining" attribute selector methods that match on substrings instead of on tokens.

Added remaining attribute matching operators and a corresponding selector method to utilize them. Refactored existing attribute-based selector methods to use this method.

Fixes #1554

Type of change

• [ ] Bugfix
• [x] Feature

Checklist

• [x] I have read the contribution guide: https://vaadin.com/docs/latest/guide/contributing/overview/
• [x] I have added a description following the guideline.
• [x] The issue is created in the corresponding repository and I have referenced it.
• [x] I have added tests to ensure my change is effective and works as intended.
• [x] New and existing tests are passing locally with my change.
• [x] I have performed self-review and corrected misspellings.

Additional for Feature type of change

• [x] Enhancement / new feature was discussed in a corresponding GitHub issue and Acceptance Criteria were created.