shwap/bitswap: Memory leak

[Wondertan]

This branch contains changes that minimized the affect for the leak, but didn't completely solved.

The main hunch is related to high peer churn, as with stable connections this is not reproducible. Also, this is demonstrated by ipfs/boxo@4becbe1, which was the commit that fixed alleviated the most pressure. This commit avoids automatic WANT_HAVE broadcast to every connected peer, relying on internal rebroadcast inside session instead.