refactor(lib): Remove uses of pin_project::project attribute (#2219)

pin-project will deprecate the project attribute due to some unfixable
limitations.

Refs: https://github.com/taiki-e/pin-project/issues/225

src/proto/h2/server.rs

@@ -5,7 +5,7 @@ use std::time::Duration;
 
 use h2::server::{Connection, Handshake, SendResponse};
 use h2::Reason;
-use pin_project::{pin_project, project};
+use pin_project::pin_project;
 use tokio::io::{AsyncRead, AsyncWrite};
 
 use super::{decode_content_length, ping, PipeToSendStream, SendBuf};
@@ -326,7 +326,7 @@ where
     state: H2StreamState<F, B>,
 }
 
-#[pin_project]
+#[pin_project(project = H2StreamStateProj)]
 enum H2StreamState<F, B>
 where
     B: HttpBody,
@@ -367,13 +367,11 @@ where
     B::Error: Into<Box<dyn StdError + Send + Sync>>,
     E: Into<Box<dyn StdError + Send + Sync>>,
 {
-    #[project]
     fn poll2(self: Pin<&mut Self>, cx: &mut task::Context<'_>) -> Poll<crate::Result<()>> {
         let mut me = self.project();
         loop {
-            #[project]
             let next = match me.state.as_mut().project() {
-                H2StreamState::Service(h) => {
+                H2StreamStateProj::Service(h) => {
                     let res = match h.poll(cx) {
                         Poll::Ready(Ok(r)) => r,
                         Poll::Pending => {
@@ -417,7 +415,7 @@ where
                         return Poll::Ready(Ok(()));
                     }
                 }
-                H2StreamState::Body(pipe) => {
+                H2StreamStateProj::Body(pipe) => {
                     return pipe.poll(cx);
                 }
             };