Fix use-after-free during lazy object initialization

[arnaud-lb]

Fixes two issues discovered by #15999:

• Object may be released during initialization. Increase the object's refcount during initialization to prevent that. If the refcount is zero after restoring it, an exception is thrown (similarly to 47ed190).
• The assigned value may be changed during initialization, so we may have to de-ref it again before forwarding the zend_std_write_property() call to the initialized object

[DanielEScherzer]

Suggest adding a test case with the reproduction case from my report in #15999

[arnaud-lb]

Indeed, I forgot to stage the test :)

[iluuu1994]

LGTM!

[iluuu1994]

Nit: Usually, the restriction to declare a variable after a label is circumvented with a ;.

Suggested change

	lazy_init:
	lazy_init:;

If you prefer braces, that's fine too.