Support php-version: preinstalled

[SystemKeeper]

Describe the feature
Most runners (be it GitHub-Hosted or Self-Hosted) have php versions pre-installed. For some workflows the performance is more important than the exact php version. So when targeting ubuntu-24.04 it makes sense to use PHP 8.3, while on ubuntu-22.04 it makes sense to use PHP 8.1. Therefore I was thinking if adding something like php-version: preinstalled or php-version: highest-preinstalled would make sense and setup-php would automatically choose the (highest) version that's already inside the image?

Version

• I have checked releases, and the feature is missing in the latest patch version of v2.

Underlying issue
Reduce bandwidth consumption and time to setup.

Describe alternatives
Manually adjust the workflows.

Additional context

Are you willing to submit a PR?
Generally yes, although no idea where to start.