Add expose_php option with reduced precision

Description

As @krakjoe pointed out at https://github.com/php/php-src/pull/3335, the popular default configurations are decided by package managers and hosting providers, and the default already has expose_php enabled.

But, we also know that those same package managers and hosting providers feel their only option is to turn this off as a sort of security through obscurity. This in turn can deminish global statistics (e.g. W3 Techs).

Perhaps we could offer a middleground that would appeal to some of the package managers (e.g. Debian, Fedora), and major hosting providers to no longer turn it off completely. For example:

X-Powered-By: PHP/8.2.9

… could be reduced to:

X-Powered-By: PHP

One could instead consider preserving major or major+minor version. But, I think an option that controls simply whether the version is obscured is more likely to receive broad adoption, and keeps the API simpler to maintain and to consume (also crawlers interpreting and aggregating this information).

/cc @Slamdunk @petk

Start by tracing the existing expose_php configuration and the response path that generates the X-Powered-By header. Compare the proposed reduced-precision behavior with the current enabled and disabled cases, then identify the relevant configuration and test entry points. Done means a supported option can retain the header while omitting its version.