T16559 router params

[niden]

Hello!

• Type: bug fix
• Link to issue: [BUG]: Router parts cannot be unset, if matches parts are optional #16559

In raising this pull request, I confirm the following:

• I have read and understood the Contributing Guidelines
• I have checked that another pull request for this purpose does not exist
• I wrote some tests for this PR
• I have updated the relevant CHANGELOG
• I have created a PR for the documentation about this change

Fixed Phalcon\Mvc\Router::handle() leaving unmatched optional named parameters (e.g. {id:(/[0-9]+)?}{slug:(/.+)?}) in the resulting params with their raw regex group positions (id => 1, slug => 2) instead of unsetting them; the unset branch was nested under else of typeof converters === "array", but Route::$converters defaults to [] so the branch was unreachable. The check is now flattened so an unmatched positional parameter is removed when no per-part converter exists

Thanks