DOMNodeList elements are accessible through array notation

Fixes #67949
Fixed a bug that causes crash when environment variable is access while parsing php.ini
Merge branch 'pr/846' into PHP-5.6

* pr/846:
  DOMNodeList elements are accessible through array notation
Updated NEWS for #67949
Merge branch 'PHP-5.6'

Conflicts:
	ext/dom/dom_properties.h
	ext/dom/nodelist.c
	ext/dom/php_dom.c
Copy all the arena allocated data from SHM to process memory at once
Directly use zend_string for php_implode/php_explode

Also drop some unnecessary zval separations and copies
Fix bug #68191: Broken reference across objects
Review a few more SEPARATE_ZVAL_IF_NOT_REF usages
Remove support for classes without class entries

get_class_entry must be non-NULL and return non-NULL.
Remove proxy object implementation
Remove get_class_entry object handler
Remove zend_get_class_entry function
Remove get_class_entry handlers in COM
Remove PDORow get_class_entry handler
zval must not be converted in place without duplication
Refactored DOMNodeList array dereferencing implementation
Merge branch 'PHP-5.6'

* PHP-5.6:
  Refactored DOMNodeList array dereferencing implementation

Conflicts:
	ext/dom/nodelist.c
	ext/dom/php_dom.c
Improved VM stack primitives for fast paths. Slow paths are not inlined anymore.
Remove Z_OBJ_CLASS_NAME_P

Doesn't make much sense anymore, now that get_class_entry is
gone.