Wasm: failure in gc.cpp find_first_object

[yowl]

Wasm can cause the assert assert (Align (size (o)) >= Align (min_obj_size)); in find_first_object in gc.cpp. When this happens size(o) == 0 and execution goes through the logic for searching the previous bricks. Also a clue perhaps is that o & 2 == 2

[yowl]

Just creating a lot of RhpNewArrayAlign8 is enough to break it.

        var mr = new MiniRandom(57);
        var keptObjects = new object[100];
        for (var i = 0; i < 1000000; i++)
        {
            var r = mr.Next();
            object o;
            o = new long[10000];
            keptObjects[r % 100] = o;
        }

[yowl]

Looks like I've passed the wrong size to RhpGcAlloc and RhpPublishObject, hopefully an easy fix

[yowl]

While the linked PR fixes the above case, this still happens when trying larger projects, e.g. starting a Uno Platform HelloWorld app