This PR updates the litep2p backend to version 0.8.1 from 0.8.0.
- Check the [litep2p updates forum
post](https://forum.polkadot.network/t/litep2p-network-backend-updates/9973/3)
for performance dashboards.
- Check [litep2p release
notes](https://github.com/paritytech/litep2p/pull/288)

The v0.8.1 release includes key fixes that enhance the stability and
performance of the litep2p library. The focus is on long-running
stability and improvements to polling mechanisms.

### Long Running Stability Improvements

This issue caused long-running nodes to reject all incoming connections,
impacting overall stability.

Addressed a bug in the connection limits functionality that incorrectly
tracked connections due for rejection.

This issue caused an artificial increase in inbound peers, which were
not being properly removed from the connection limit count.

This fix ensures more accurate tracking and management of peer
connections [#286](https://github.com/paritytech/litep2p/pull/286).

### Polling implementation fixes

This release provides multiple fixes to the polling mechanism, improving
how connections and events are processed:
- Resolved an overflow issue in TransportContext’s polling index for
streams, preventing potential crashes
([#283](https://github.com/paritytech/litep2p/pull/283)).
- Fixed a delay in the manager’s poll_next function that prevented
immediate polling of newly added futures
([#287](https://github.com/paritytech/litep2p/pull/287)).
- Corrected an issue where the listener did not return Poll::Ready(None)
when it was closed, ensuring proper signal handling
([#285](https://github.com/paritytech/litep2p/pull/285)).


### Fixed

- manager: Fix connection limits tracking of rejected connections
([#286](https://github.com/paritytech/litep2p/pull/286))
- transport: Fix waking up on filtered events from `poll_next`
([#287](https://github.com/paritytech/litep2p/pull/287))
- transports: Fix missing Poll::Ready(None) event from listener
([#285](https://github.com/paritytech/litep2p/pull/285))
- manager: Avoid overflow on stream implementation for
`TransportContext`
([#283](https://github.com/paritytech/litep2p/pull/283))
- manager: Log when polling returns Ready(None)
([#284](https://github.com/paritytech/litep2p/pull/284))


### Testing Done

Started kusama nodes running side by side with a higher number of
inbound and outbound connections (500).
We previously tested with peers bounded at 50. This testing filtered out
the fixes included in the latest release.

With this high connection testing setup, litep2p outperforms libp2p in
almost every domain, from performance to the warnings / errors
encountered while operating the nodes.

TLDR: this is the version we need to test on kusama validators next

- Litep2p

Repo            | Count      | Level      | Triage report
-|-|-|-
polkadot-sdk | 409 | warn | Report .*: .* to .*. Reason: .*. Banned,
disconnecting. ( Peer disconnected with inflight after backoffs. Banned,
disconnecting. )
litep2p | 128 | warn | Refusing to add known address that corresponds to
a different peer ID
litep2p | 54 | warn | inbound identify substream opened for peer who
doesn't exist
polkadot-sdk | 7 | error |  Called `on_validated_block_announce` with a
bad peer ID .*
polkadot-sdk    | 1          | warn       |  Error while dialing .*: .*
polkadot-sdk | 1 | warn | Report .*: .* to .*. Reason: .*. Banned,
disconnecting. ( Invalid justification. Banned, disconnecting. )

- Libp2p

Repo            | Count      | Level      | Triage report
-|-|-|-
polkadot-sdk | 1023 | warn |  Ignored block \(#.* -- .*\) announcement
from .* because all validation slots are occupied.
polkadot-sdk | 472 | warn | Report .*: .* to .*. Reason: .*. Banned,
disconnecting. ( Unsupported protocol. Banned, disconnecting. )
polkadot-sdk | 379 | error |  Called `on_validated_block_announce` with
a bad peer ID .*
polkadot-sdk | 163 | warn | Report .*: .* to .*. Reason: .*. Banned,
disconnecting. ( Invalid justification. Banned, disconnecting. )
polkadot-sdk | 116 | warn | Report .*: .* to .*. Reason: .*. Banned,
disconnecting. ( Peer disconnected with inflight after backoffs. Banned,
disconnecting. )
polkadot-sdk | 83 | warn | Report .*: .* to .*. Reason: .*. Banned,
disconnecting. ( Same block request multiple times. Banned,
disconnecting. )
polkadot-sdk | 4 | warn | Re-finalized block #.* \(.*\) in the canonical
chain, current best finalized is #.*
polkadot-sdk | 2 | warn | Report .*: .* to .*. Reason: .*. Banned,
disconnecting. ( Genesis mismatch. Banned, disconnecting. )
polkadot-sdk | 2 | warn | Report .*: .* to .*. Reason: .*. Banned,
disconnecting. ( Not requested block data. Banned, disconnecting. )
polkadot-sdk | 2 | warn | Can't listen on .* because: .*
polkadot-sdk    | 1          | warn       | 

 Error while dialing .*: .*

---------

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>