Fix serialization of RC1 objects appearing in object graph twice

Previously, if an object had RC1 it would never be recorded in
php_serialize_data.ht because it was assumed that it could

Fix serialization of RC1 objects appearing in object graph twice

Previously, if an object had RC1 it would never be recorded in
php_serialize_data.ht because it was assumed that it could not be encountered
again. This assumption is incorrect though as the object itself may be saved
inside an array with RCn. This results in a new instance of the object, instead
of a second reference to the same object.

This is solved by tracking these objects in php_serialize_data.ht. To retain
performance, track if the current object resides in a potentially nested RCn
array. If not, and if the object is RC1 itself it may be omitted from
php_serialize_data.ht.

Additionally, we may treat the array root itself as RC1 because it may not
appear in the object graph again without recursion. Recursive arrays are still
somewhat broken even with this change, as the tracking of the array only happens
when the reference is encountered, thus resulting in a -> a' -> a' for a self
recursive array a -> a. Recursive arrays have limited support in serialize
anyway, so we ignore this case for now.

Co-authored-by: Dmitry Stogov <dmitry@zend.com>
Co-authored-by: Martin Hoch <martin@littlerobot.de>

Closes GH-11349
Closes GH-11305

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