Perform atomic updates

[monoid-is-a-monad]

The updates should be performed in an atomic way:
if any part of the update fails, the whole update should fail and the intermediate changes reverted

[monoid-is-a-monad]

It seems the leveraging the existing TRANSACTIONS and COMMITs is feasible.
The current limitations in transactions are the following:
https://cloud.google.com/bigquery/docs/transactions#limitations

Ran the following query and it was successfully rolled back:

  BEGIN TRANSACTION;

-- 3,210
   INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

-- 3,210
   INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

-- 3,210
   INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

-- 3,210
   INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

   INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

   INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

   INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;
  
     INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

      INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

      INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

      INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

      INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

      INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

      INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

      INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

      INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

      INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

      INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

      INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;

      INSERT INTO db_sync.test_tx
   SELECT * FROM db_sync.tmp_tx_1;
   
   RAISE USING message= "Intentional Failure";

   COMMIT TRANSACTION;

also run the following tests that use much bigger tables (each csv is ~130MB):

  BEGIN TRANSACTION;

--  343,387
   INSERT INTO db_sync.test_rel_addr_txout
   SELECT * FROM db_sync.tmp_rel_addr_txout_1;

--  343,387
      INSERT INTO db_sync.test_rel_addr_txout
   SELECT * FROM db_sync.tmp_rel_addr_txout_1;
RAISE USING message= "Intentional Failure";
      INSERT INTO db_sync.test_rel_addr_txout
   SELECT * FROM db_sync.tmp_rel_addr_txout_1;

      INSERT INTO db_sync.test_rel_addr_txout
   SELECT * FROM db_sync.tmp_rel_addr_txout_1;
   
      INSERT INTO db_sync.test_rel_addr_txout
   SELECT * FROM db_sync.tmp_rel_addr_txout_1;
   COMMIT TRANSACTION;