Problem: wallet sync logic is not compatible with the refactored tendermint-rs light client design

[yihuang]

When thinking about #828 and trying to incorporate the new light client design of tendermint-rs, I think our wallet sync logic should be overhauled too.

• light client from tendermint-rs handled the all the light client sync and verification now, including all the disk and network io, running in standalone thread.
• it supports multiple peers, a big step on Problem: client currently only works against a single node #1114.
• the light client sync process can be shared by different wallets.

wallet sync logic will be like this:

let light_client_handle = get_shared_light_client_handle_or_spawn();
let light_block = light_client_handle.verify_to_highest();
// download blocks and sync wallet states
// can safely do batch and fast forward here
// still need to verify block hash and app hashes and the chain
// and verify last block matches the light_block
// only persist wallet state after synced to the last block
set wallet.trusted to false
sync_untrusted_to(light_block.height, light_block.app_hash);
check hashes match with light_block
set wallet.trsuted to true