Improve Network Spans (#2169)

* utility functions for erasure-coding threshold

* add candidate-hash tag to candidate jaeger spans

* debug implementation for jaeger span

* add a span to each live candidate in availability dist.

* availability span covers only our piece

* fix tests

* keep span alive slightly longer

* remove spammy bitfield-gossip-received log

* Revert "remove spammy bitfield-gossip-received log"

This reverts commit 831a2db5

.

* add claimed validator to bitfield-gossip span

* add peer-id to handle-incoming span

* add peer-id to availability distribution span

* Update node/network/availability-distribution/src/lib.rs

Co-authored-by: Bernhard Schuster <[email protected]>

* Update erasure-coding/src/lib.rs

Co-authored-by: Bernhard Schuster <[email protected]>

* Update node/subsystem/src/jaeger.rs

Co-authored-by: Bernhard Schuster <[email protected]>

Co-authored-by: Bernhard Schuster <[email protected]>