fix: controller attribute filters with parameters

[michalsn]

Description
This PR fixes an issue with controller attribute filters that use parameters. See: #9745 (comment)

Filter parameters are always declared as strings elsewhere in the framework, and there is no supported way to handle them differently. See:

• https://codeigniter.com/user_guide/incoming/routing.html#filter-arguments
• https://codeigniter.com/user_guide/incoming/filters.html#filter-arguments

To maintain consistency, this change ensures that filter parameters are treated as strings, matching the existing convention. Any other behavior would introduce inconsistency.

All existing tests have been kept, even those that may not make much sense in this context, to serve as examples of how filters handle mixed-type parameters (they are converted to strings).

This change only affects Filters - everything else will continue to behave as before.

Checklist:

• Securely signed commits
• Component(s) with PHPDoc blocks, only if necessary or adds value (without duplication)
• Unit testing, with >80% coverage
• User guide updated
• Conforms to style guide

[lonnieezell]

My bad for the bad example in the docs. That was definitely an oops on my part.

But this solution seems good. I don't see any issues, and allows a little more flexibility on the user end.

[datamweb]

@michalsn Thanks!