Parachain inherent checks on relay validators

[akru]

Description
Let's imagine a situation where the collator produces a block with the wrong timestamp inherent, let it be far in the future. In that case, other collators can't include these blocks because of failed inherent checks. But validators of the relay chain can include these blocks into the relay chain, right?

If a block with the wrong timestamp inherent acceptable by relay validators, then the parachain could be attacked by anyone with wrong inherent, and block production will be stoped.

[akru]

@bkchr Is this attack vector connected to #343?

[bkchr]

This is the same as #343.

[akru]

Got it, thank you @bkchr!