feat(consensus/grandpa): Add warp sync proof verification

[dimartiro]

Changes

Implement warp sync proof verification.
The warp proof is verified by traversing the warp proof fragments (with the block headers and justifications), then we verify the justifications against the authorities based on the genesis authorities and the scheduled changes.
If we are able to verify all the fragments, then the warp proof is valid.

• Add warp sync proof verify method
• Minor fixes in proof generation
• Use right grandpa types
• Tests
  • Improve tests
  • Test both proof generation and verification

Reference parity code

Note: I'd rather to not use generics in this initial phase because that will imply more changes (eg: in BlockState and GrandpaState) we can revisit this later to make the structs generic.

Tests

make test

Issues

#4237

[timwu20]

Do you mind moving the internal/client/consensus/grandpa/warp_sync.go file to lib/grandpa package? I think this is more inline with the "old" way of doing this with the local interfaces for the older block BlockState and GrandpaState. I'd like to keep things more analogous to substrate in the internal/primitives and internal/client code.

[dimartiro]

Do you mind moving the internal/client/consensus/grandpa/warp_sync.go file to lib/grandpa package? I think this is more inline with the "old" way of doing this with the local interfaces for the older block BlockState and GrandpaState. I'd like to keep things more analogous to substrate in the internal/primitives and internal/client code.

Moved!