fix: improve CURLRequest intermediate HTTP response handling

[michalsn]

Description
This PR fixes a bug in CURLRequest where intermediate HTTP responses were not properly removed from the response chain in certain scenarios, causing incorrect status codes and headers to be returned instead of the final response.

The problem was that the original logic processed different types of intermediate responses separately, which could miss responses that appeared in mixed order.

• Refactored send() method to use unified intermediate response removal
• Removed handleRedirectHeaders() private method
• Added removeIntermediateResponses() and shouldRemoveCurrentResponse() private methods, which now handle the entire process of intermediate headers removal

The issue was reported on the forum: https://forum.codeigniter.com/showthread.php?tid=93094&pid=426075#pid426075

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

[michalsn]

Thank you @paulbalandan