Do not use grpid to find last inserted row in chats table

Instead, use last_insert_rowid() function to find the row.

There is no race condition in using last_insert_rowid(), because
last_insert_rowid() returns row id last inserted in this connection. As
we hold the connection during the whole transaction, it is impossible
that some other thread will execute INSERT statement in parallel.

This commit is part of the effort to get rid of sql::get_rowid hack and
use transactions more for related SQL statements.

src/sql.rs

@@ -893,6 +893,11 @@ fn open(
             )?;
             sql.set_raw_config_int(context, "dbversion", 62)?;
         }
+        if dbversion < 63 {
+            info!(context, "[migration] v63");
+            sql.execute("UPDATE chats SET grpid='' WHERE type=100", NO_PARAMS)?;
+            sql.set_raw_config_int(context, "dbversion", 63)?;
+        }
 
         // (2) updates that require high-level objects
         // (the structure is complete now and all objects are usable)