* PVD: `block_number`->`relay_parent_number`
* ValidationParams: `relay_chain_height`->`relay_parent_number`
* Expose DMQ MQC hash as a well-known-key
This way the relay storage merkle proofs will be able to obtain the DMQ
MQC hash and we will be able to remove the it from the
PersistedValidationData struct.
* PersistedValidationData: Remove HRMP MQC heads
* PersistedValidationData: Remove `dmq_mqc_head`
* Expose the HRMP ingress channel index as a well-known-key
This way a parachain (PVF and collator) can find all the parachains that
have an outbound channel to the given one. That allows in turn to find
all the inbound channels for the given para.
Having access to that allows the parachain to get the same information
as the hrmp_mqc_heads now provide.
* Rename `relay_storage_root` to `relay_parent_storage_root`
* Adds message types
* Add code skeleton
* Adds subsystem code.
* Adds a first test
* Adds interaction result to availability_lru
* Use LruCache instead of a HashMap
* Whitespaces to tabs
* Do not ignore errors
* Change error type
* Add a timeout to chunk requests
* Add custom errors and log them
* Adds replace_availability_recovery method
* recovery_threshold computed by erasure crate
* change core to std
* adds docs to error type
* Adds a test for invalid reconstruction
* refactors interaction run into multiple methods
* Cleanup AwaitedChunks
* Even more fixes
* Test that recovery with wrong root is an error
* Break to launch another requests
* Styling fixes
* Add SessionIndex to API
* Proper relay parents for MakeRequest
* Remove validator_discovery and use message
* Remove a stream on exhaustion
* On cleanup free the request streams
* Fix merge and refactor
Sergei Shulepov