feat: add Connection::shrink_buffers, PoolConnection::close

closes #2372

sqlx-sqlite/src/any.rs

@@ -59,6 +59,10 @@ impl AnyConnectionBackend for SqliteConnection {
         SqliteTransactionManager::start_rollback(self)
     }
 
+    fn shrink_buffers(&mut self) {
+        // NO-OP.
+    }
+
     fn flush(&mut self) -> BoxFuture<'_, sqlx_core::Result<()>> {
         Connection::flush(self)
     }

sqlx-sqlite/src/connection/mod.rs

@@ -157,6 +157,11 @@ impl Connection for SqliteConnection {
         })
     }
 
+    #[inline]
+    fn shrink_buffers(&mut self) {
+        // No-op.
+    }
+
     #[doc(hidden)]
     fn flush(&mut self) -> BoxFuture<'_, Result<(), Error>> {
         // For SQLite, FLUSH does effectively nothing...