tracers: leaks: fix potentially invalid memory access when trying to detect object...

tracers: leaks: fix potentially invalid memory access when trying to detect object type

The is_gst_mini_object_check would sometimes detect a proper GObject
as a mini object, and then bad things happen.

We know whether a pointer is a proper GObject or a MiniObject here
though, so just pass that information to the right code paths and
avoid the heuristics altogether.

Eliminates all remaining uses of object_is_gst_mini_object().

Fixes #1334

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/2832>