Use GAT in volo-grpc `SendEntryMessage`

[LYF1999]

Feature Request

Crates

Motivation

The definition of SendEntryMessage can be better with GAT

pub trait SendEntryMessage {
    fn into_body(
        self,
        compression_config: Option<CompressionEncoding>,
    ) -> crate::BoxStream<'static, Result<Bytes, crate::Status>>;
}

with GAT

pub trait SendEntryMessage {
    type Body: Stream<Item = Result<Bytes, crate::Status>> + Send
    fn into_body(
        self,
        compression_config: Option<CompressionEncoding>,
    ) -> Self::Body;
}