Automate removal of unused PHP `use` statements

[Soean]

Describe your use case and the problem you are facing

Currently, the codebase contain unused PHP use statements, which can clutter the code and increase the maintenance burden. Manually identifying and removing these is inefficient and prone to human error.

To streamline our workflow and ensure consistency across all packages using wp-cli-tests, I propose automating the detection and removal of unused imports.

Describe the solution you'd like

Integrate the Slevomat Coding Standard with a specific focus on the UnusedUses rule. This is a battle-tested tool that works seamlessly with PHP_CodeSniffer.

Target Rule:
SlevomatCodingStandard.Namespaces.UnusedUses