feat(l4): make Stream::rewind() public for protocol detection

Make the rewind() method public so that PreTlsProcess implementations
can put data back onto the stream when the data doesn't match the
expected protocol signature.

This is needed for PROXY protocol detection where the pre-TLS handler
reads initial bytes to check for the PROXY signature, and must rewind
if the data is not PROXY protocol so TLS can proceed normally.

Author: jaw-sh

pingora-core/src/protocols/l4/stream.rs

@@ -445,8 +445,11 @@ impl Stream {
         Ok(())
     }
 
-    /// Put Some data back to the head of the stream to be read again
-    pub(crate) fn rewind(&mut self, data: &[u8]) {
+    /// Put some data back to the head of the stream to be read again.
+    ///
+    /// This is useful when you've read data to detect a protocol (e.g., PROXY protocol)
+    /// but the data wasn't what you expected, so you need to "unread" it.
+    pub fn rewind(&mut self, data: &[u8]) {
         if !data.is_empty() {
             self.rewind_read_buf.push(data.to_vec());
         }