rpc: WebSocket client cannot parse NewBlock events

[romac]

As of c8b97aa, and the addition of the time_iota_ms field to tendermint::block::Size, the WebSocket client cannot parse NewBlock events emitted by Tendermint because those do not include the time_iota_ms in the appropriate place.

As the time_iota_ms field is not part of Size's Protobuf counterpart, the value of this field is currently hardcoded to 1000 in the Proto->Domain conversion.

The field should probably be either removed or be added a #[serde(default = "...")] annotation so that we can parse NewBlock events again.

Steps to reproduce

1. Start a Tendermint node which exposes a WS server at ws://127.0.0.1:26657/websocket (eg. via ibc-rs dev-env script`)
2. Check out the romac/ws-inspect branch of tendermint-rs
3. $ cd tools/ws-inspect
4. $ RUST_LOG=info cargo run
5. Notice that we receive raw NewBlock events over the WebSocket connection but that those fail to parse because of the missing time_iota_ms field

[/Users/coromac/Informal/Code/Current/tendermint-rs/rpc/src/client/transport/websocket.rs:648] &msg = "{\n  \"jsonrpc\": \"2.0\",\n  \"id\": \"cf395ae4-3d9b-4076-b847-ef6e7661184e\",\n  \"result\": {\n    \"query\": \"tm.event = 'NewBlock'\",\n    \"data\": {\n      \"type\": \"tendermint/event/NewBlock\",\n      (...snip...)"
[/Users/coromac/Informal/Code/Current/tendermint-rs/rpc/src/client/transport/websocket.rs:648] Event::from_string(&msg) = Err(
    Error {
        code: ParseError,
        message: "Parse error. Invalid JSON",
        data: Some(
            "missing field `time_iota_ms` at line 230 column 13",
        ),
    },
)