fix: mark blocking invocations of flush! as @blocking

sqlx-postgres/src/connection/executor/execute.rs

@@ -77,7 +77,7 @@ impl<Rt: Runtime> PgConnection<Rt> {
         Rt: sqlx_core::blocking::Runtime,
         E: Execute<'q, 'a, Postgres>,
     {
-        flush!(self);
+        flush!(@blocking self);
         impl_execute!(@blocking self, query)
     }
 }

sqlx-postgres/src/connection/executor/fetch_all.rs

@@ -83,7 +83,7 @@ impl<Rt: Runtime> PgConnection<Rt> {
         Rt: sqlx_core::blocking::Runtime,
         E: Execute<'q, 'a, Postgres>,
     {
-        flush!(self);
+        flush!(@blocking self);
         impl_fetch_all!(@blocking self, query)
     }
 }

sqlx-postgres/src/connection/executor/fetch_optional.rs

@@ -91,7 +91,7 @@ impl<Rt: Runtime> PgConnection<Rt> {
         Rt: sqlx_core::blocking::Runtime,
         E: Execute<'q, 'a, Postgres>,
     {
-        flush!(self);
+        flush!(@blocking self);
         impl_fetch_optional!(@blocking self, query)
     }
 }

sqlx-postgres/src/protocol/frontend/terminate.rs

@@ -26,7 +26,7 @@ mod tests {
         let mut buf = Vec::new();
         Terminate.serialize(&mut buf)?;
 
-        assert_eq!(&buf, &[b'X']);
+        assert_eq!(&buf, &[b'X', 0, 0, 0, 4]);
 
         Ok(())
     }