fix int formatting in std::collections::object

[Renerick]

Reported at https://discord.com/channels/650345951868747808/650347464498610189/1291898838772088832

When the value is a signed integer, it's still formatted as unsigned integer:

io::printn(b_value.type.kindof);
io::printn(b_value);
io::printn((int128)b_value.i);

SIGNED_INT
340282366920938463463374607431768211414
-42

[lerno]

Ideally there is also a note in the releasenotes for this, but I'm going to accept this as is. But something to think about in the future.

[lerno]

Thank you!