Block weight ChainAPI (#3301)

* guide: ChainApiMessage::BlockWeight

* node: BlockWeight ChainAPI

* fix compile issue

* implement ChainApi::BlockWeight

* add test for ChainApi::BlockWeight

* update substrate

Co-authored-by: André Silva <andrerfosilva@gmail.com>
11 jobs for master in 37 minutes and 1 second (queued for 2 seconds)