Make OPcache non-optional

[arnaud-lb]

Spun of #18660

RFC: https://wiki.php.net/rfc/make_opcache_required

Currently, OPcache is both a Zend extension and a PHP module, but it must be loaded as a Zend extension with zend_extension=opcache.so. The Zend extension then loads the PHP module. Also, OPcache can not be built statically.

This PR makes the following changes:

• Make OPcache non-optional: OPcache is always built into the binary
• Since the mechanism for loading builtin extensions supports PHP modules, not Zend extensions: Reversed the roles of the Zend extension and PHP module so that the PHP module loads the Zend extension.

Depends on #18939.

[dstogov]

In my opinion opcache is not always necessary and even may add troubles in some cases (e.g. routers and media servers). I know dune-hd used PHP in their firmwares. Very probably other players powered by MPD. Installing PHP on routers running under *WRT is a common practice.

Technically I don't see problems in the patch.

[arnaud-lb]

@dstogov do you remember what kind troubles it caused? Was it related to code size, memory usage, or something else? Note that the RFC forces opcache to be built and linked into the binary, but it doesn't set opcache.enable.

[dstogov]

@dstogov do you remember what kind troubles it caused? Was it related to code size, memory usage, or something else? Note that the RFC forces opcache to be built and linked into the binary, but it doesn't set opcache.enable.

No. I wrote - "this may add troubles". In the best case this will just waste ~1MB of RAM.