This PR should supersede
https://github.com/paritytech/polkadot-sdk/pull/2814 and accomplish the
same with less changes. It's needed to run sync strategies in parallel,
like running `ChainSync` and `GapSync` as independent strategies, and
running `ChainSync` and Sync 2.0 alongside each other.
The difference with https://github.com/paritytech/polkadot-sdk/pull/2814
is that we allow simultaneous requests to remote peers initiated by
different strategies, as this is not tracked on the remote node in any
way. Therefore, `PeerPool` is not needed.
CC @skunert
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Co-authored-by: Sebastian Kunert <skunert49@gmail.com>
Dmitry Markin