Conflict between batch transactions and mandatory headers from on-demand transactions

[svyatonik]

So right now when we need to deliver messages, we craft batch transaction which includes the proof of relay chain header, parachain header and proof of messages. If at the same time on-demand relay wants to submit mandatory header, one of transactions may fail (it'll be invalidated before including into the block). We need to coordinate submissions between two relay tasks.

This isn't super critical, because mandatory headers are rare on production chains, but it is still an issue.

Also this (needs investigating) may be a reason of the following error I've seen couple of times:

[BridgeHubRococo_to_BridgeHubWococo_MessageLane_00000001] 2023-05-15 07:28:28 +00 ERROR bridge Error asking for source headers at BridgeHubRococo::ReceivingConfirmationsDelivery: Custom("Failed to optimize Wococo GRANDPA jutification for header HeaderId(45, 0x8c616b5441956c6f249c51c90537f1aebfd695661c2b87c69d8c68fda503b64c): Error::InvalidAuthoritySignature"). Retrying in 0.478781692

[svyatonik]

superseded by #3002