Fix CI: move h2 response_fields before its test module; qualify TlsStream doc link

- clippy::items_after_test_module: h2/conn.rs declared response_fields after the
  #[cfg(test)] mod, which `cargo clippy --all-targets -D warnings` rejects.
- rustdoc broken-intra-doc-link: session.rs `[`TlsStream`]` now points at
  crate::tls::TlsStream (it isn't in scope at that doc site).

Verified with the exact CI commands: clippy --all-targets --all-features
-D warnings and RUSTDOCFLAGS=-D warnings cargo doc --all-features both pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: MagicalTux

src/h2/conn.rs

@@ -568,6 +568,15 @@ impl H2Conn {
     }
 }
 
+/// Build the HPACK field list for a response from the shared response-header
+/// rules (`:status` first, hop-by-hop dropped, `server` defaulted).
+fn response_fields(status: StatusCode, headers: &Headers, server: Option<&str>) -> Vec<HeaderField> {
+    crate::proto::response_fields(status, headers, server)
+        .iter()
+        .map(|(n, v)| HeaderField::new(n, v))
+        .collect()
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
@@ -684,16 +693,3 @@ mod tests {
         assert!(c.wants_close());
     }
 }
-
-/// Build the HPACK field list for a response from the shared response-header
-/// rules (`:status` first, hop-by-hop dropped, `server` defaulted).
-fn response_fields(
-    status: StatusCode,
-    headers: &Headers,
-    server: Option<&str>,
-) -> Vec<HeaderField> {
-    crate::proto::response_fields(status, headers, server)
-        .iter()
-        .map(|(n, v)| HeaderField::new(n, v))
-        .collect()
-}

src/session.rs

@@ -132,8 +132,9 @@ impl Session {
         }
     }
 
-    /// Create a TLS (HTTPS) session wrapping an accepted [`TlsStream`]. The
-    /// protocol (HTTP/1.1 or HTTP/2) is chosen once ALPN is known.
+    /// Create a TLS (HTTPS) session wrapping an accepted
+    /// [`TlsStream`](crate::tls::TlsStream). The protocol (HTTP/1.1 or HTTP/2)
+    /// is chosen once ALPN is known.
     #[cfg(feature = "tls")]
     pub fn tls(cfg: SessionConfig, stream: crate::tls::TlsStream) -> Session {
         Session {