Bug: GC of a fiber suspended in a file included from a function

[EdmondDantes]

A file included from a function, or code eval'd in it, runs in its own frame over the symbol table of that function. zend_fiber_object_gc() walks the suspended fiber's frames and adds the symbol table of each one, so a fiber suspended inside such a file added the same table twice: the collector counted its values twice and decremented their refcounts below zero.

Reproduction (debug build, no extensions):

// inc.php: $local = new stdClass; Fiber::suspend(); echo "kept\n";
function run() { include __DIR__ . '/inc.php'; }
 
$fiber = new Fiber(function () { run(); });
$fiber->start();
 
$holder = new stdClass;
$holder->fiber = $fiber;
$holder->self = $holder;
unset($holder);
 
gc_collect_cycles();
$fiber->resume();

Expected: kept. Actual: zend_gc_delref: Assertion 'p->refcount > 0' failed (debug build).

The fix skips a frame whose symbol table is the one the previous frame already added. No behaviour change otherwise.

Test: Zend/tests/fibers/gc-include-shared-symbol-table.phpt (aborts on PHP-8.4 debug without the fix, passes with it; Zend/tests/fibers 97 of 97 pass). The test relies on the debug assertion, so only debug builds detect the bug.