The string added had uninitialized memory due to
php_read_stream_all_chunks() not moving the buffer position, resulting
in the same data always being overwritten instead of new data being
added to the end of the buffer.

Closes GH-20592.

* PHP-8.3:
  Fix GH-20584: Information Leak of Memory
  Fix GH-20583: Stack overflow in http_build_query via deep structures

* PHP-8.4:
  Fix GH-20584: Information Leak of Memory
  Fix GH-20583: Stack overflow in http_build_query via deep structures

* PHP-8.5:
  Fix GH-20584: Information Leak of Memory
  Fix GH-20583: Stack overflow in http_build_query via deep structures