Before the validator only send the keys if it was updated and thus the
collators would "never" be informed about the key of the validator.

Up to now consensus instances used the main channel to communicate with
the background network worker. This lead to a race condition when
sending a local collation and dropping the router before driving the
send local collation future until it is finished. This pr changes the
communication between worker and the instances to use their own
channels. This has the advantage that we don't need an extra
`DropConsensusNetworking` message as the network is dropped
automatically when the last sender is dropped.

* add pov-block gossip message to network

* tests for pov-block gossip

* integrate pov-block gossip into main protocol

* message validation fetches pov blocks

* remove stray dbg! invocation

* test that pov-block is fetched from relay-parent topic

* Companion pr for substrate#5448

* Update Substrate reference

* Adds a SigningContext type

* Bump spec versions

* Fixes requested changes

* Bump ParachainHost api_version and guard signing_context call

* Improve error message

* If there is no signing_context api use default value

Co-authored-by: Robert Habermeier <rphmeier@gmail.com>

* move protocol.rs into subfolder

* add trait for mocking network behavior

* add a mock version of network ops

* remove some redundant parameters from service messages

* ensure fetching erasure chunks automatically cancels

* introduce dummy ProvideRuntimeApi

* abstract over gossip somewhat

* add mock gossip handler

* skeleton test

* remove dependence of shared table on router

* remove worker dependence on its own sender

* test shutdown

* add tests

* test that gossip streams are cleaned up correctly

* refactor worker out into its own struct and reduce bound on executor

* remove reliance of tests on global thread pool