Optimize phpfpm opcache: more aggressive caching, enable JIT

[patschi]

Contribution Guidelines

• I've read the contribution guidelines and wholeheartedly agree them

What does this PR include?

Short Description

This implements two things:

1. More persistent, aggressive caching by using opcache.validate_timestamps=0. This results in local PHP files never being re-validated for changes. As there are no manual changes to PHP files expected in production, that should be fine. During updates the phpfpm container will be restarted nonetheless, hence cache cleared.
2. Enabling opcache-jit, which has been introduced back in PHP 8.0. It is compiling frequently used PHP opcodes into machine code and allows for faster execution in subsequent runs.

Affected Containers

phpfpm

Did you run tests?

What did you tested?

Clicked through UI, noticed some speed improvements and no issues.

What were the final results? (Awaited, got)

See above.