fix: enhance Logger PSR-3 compliance and interpolation reliability

[gr8man]

Description
This PR addresses several issues in the Logger::interpolate() method regarding PSR-3 compliance and interpolation robustness. Based on the community discussion here, passing an array or an unstringable object inside the $context array previously caused PHP E_WARNINGs (Array to string conversion or Object ... could not be converted to string) when parsed through strtr(). PSR-3 specifies that the context array can contain anything, so the logger should handle these types gracefully.
Key Changes:

1. Array and Object Context Handling: Checks if a context value is_array() or is an unstringable object (is_object() without __toString()). If so, gracefully formats it using print_r($val, true) before interpolating, preventing runtime warnings.
2. \Stringable Interface Support: The $message argument now correctly supports PHP 8.0 \Stringable objects, safely casting them to strings.
3. Multiple Environment Variables: Replaced preg_match with preg_match_all when evaluating {env:foo} tags. Previously, only the very first environment variable tag in a log message was parsed. Now, multiple tags within the same message (e.g. {env:foo} and {env:baz}) are accurately matched and interpolated.
   Related issue/discussion: https://forum.codeigniter.com/showthread.php?tid=94242
   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

[memleakd]

Duplicate of #10384