added UploadedFile::getClientPath()

[timbatt]

Enables access to the full_path index (added in PHP 8.1) for files in directory uploads.

Description
Add the file's full_path value to UploadedFile, accessible via UploadedFile::getClientPath().
If PHP version is below 8.1 then UploadedFile::getClientPath() returns null.

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

[timbatt]

This is my first PR ever, so I am new to the process.
Please feel free to point me in the right direction if I missed anything in the PR process.

[iRedds]

follow https://github.com/codeigniter4/CodeIgniter4/tree/develop/contributing

[kenjis]

Thank you for sending PR.

1. You need to sign your commits. https://github.com/codeigniter4/CodeIgniter4/blob/develop/contributing/pull_request.md#signing
2. This PR is an enhancement. So you must send it to 4.4 branch. https://github.com/codeigniter4/CodeIgniter4/blob/develop/contributing/workflow.md#if-you-sent-to-the-wrong-branch

And please fix all errors in GitHub Action checks.
If you have any questions, feel free to ask.

[timbatt]

Ok, will do. Thanks!