Migrate skip checks to --EXTENSIONS--, p2

For rationale, see https://github.com/php/php-src/pull/6787

Make extension checks lowercase, add a special case for opcache
that has in

Migrate skip checks to --EXTENSIONS--, p2

For rationale, see https://github.com/php/php-src/pull/6787

Make extension checks lowercase, add a special case for opcache
that has internal name not matching .so filename.

Extensions migrated in part 2:
* dom
* exif
* fileinfo
* ffi

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Merge branch 'PHP-7.4' into PHP-8.0

* PHP-7.4:
Fix #77961: finfo_open crafted magic parsing SIGABRT

Fix #77961: finfo_open crafted magic parsing SIGABRT

libmagic may abort the running process, which is not desirable for PHP;
we raise a fatal error instead.

Closes GH-6437.