Consider removing maxContiguousHeight from x/blockdb

[DracoLi]

Context and scope

We are currently tracking the maximum contiguous height in x/blockdb. However, this may not be necessary for the VMs to integrate with blockdb.
It could enhance performance during bootstrapping by quickly identifying missing blocks in the database, but I have not explored this in depth yet. We should evaluate whether we can use maxContiguousHeight in the VMs to improve blockdb performance or in the Snowman bootstrapping process. If it is unnecessary, we should remove it from blockdb to simplify the implementation.

For additional context, see #4027 (comment).