[ext/standard] Move min/max array fallback into array.c

[mehmetcansahin]

Follow-up to @Girgias' review on #22127: this splits out the behavior-preserving baseline refactor before the numeric min()/max() fast path work.

Split out from #22127 as the behavior-preserving baseline refactor requested during review.

This moves the generic min()/max() array fallback out of the Zend HashTable API and into ext/standard/array.c, where it is the only remaining user. The local helper uses the regular ZEND_HASH_FOREACH_VAL() API and calls zend_compare() directly, avoiding the previous function-pointer wrapper.

UPGRADING.INTERNALS is updated to document that zend_hash_minmax() is no longer exposed.

Compatibility check: Sourcegraph search only found stale vendored/documentation copies plus one old PHP 7.x extension (viest/php-ext-collection) using this internal symbol. The removal is documented in UPGRADING.INTERNALS.

Tested with:

• make -j"$(sysctl -n hw.ncpu)"
• sapi/cli/php run-tests.php -q ext/standard/tests/array/min*.phpt ext/standard/tests/array/max*.phpt

[mehmetcansahin]

@TimWolla When you have a chance, could you take a look at this one? It has been approved by @Girgias and the checks are green.

This is the behavior-preserving baseline refactor split out before #22127.