Fix Websocket subscriptions

[ChronosXYZ]

Problem

Websocket event subscription doesn't work. Events are not received through the subscription sink though they are received by the websocket driver.

Solution

This PR ports fix for subscription router from informalsystems/tendermint-rs#1433. Also I found deserialization error when we try to parse received event, because CometBFT node sends null in data.results_finalize_block.validator_updates field instead of empty array. I fixed that by using a custom deserialization function.