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

首先跟踪现有的 expose_php 配置以及生成 X-Powered-By 标头的响应路径。将提议的降低精度行为与当前启用和禁用的情况进行比较，然后确定相关的配置和测试入口点。当某个受支持的选项可以保留标头但省略其版本时，即表示完成。