Handle edge case involving blocks not being found in the db

If there is a backfill followed by an error, logs get written to the
db but no blocks. This will make the logpoller (or backup log poller)
rely on the chain next time instead of the db to determine
lastFinalizedBlock, which could result in a gap in logs processed.
Fixing this by writing the last block in the backfil to the db along
with the logs. Its lastFinalizedBlock field will be set to its own
block number + 1, so if the db crashes it should start by pulling
the logs from that one.

core/chains/evm/logpoller/log_poller.go

@@ -679,7 +679,7 @@ func (lp *logPoller) backfill(ctx context.Context, start, end int64) error {
 		}
 
 		lp.lggr.Debugw("Backfill found logs", "from", from, "to", to, "logs", len(gethLogs), "blocks", blocks)
-		err = lp.orm.InsertLogs(convertLogs(gethLogs, blocks, lp.lggr, lp.ec.ConfiguredChainID()), pg.WithParentCtx(ctx))
+		err = lp.orm.InsertLogsWithBlock(convertLogs(gethLogs, blocks, lp.lggr, lp.ec.ConfiguredChainID()), blocks[len(blocks)-1], pg.WithParentCtx(ctx))
 		if err != nil {
 			lp.lggr.Warnw("Unable to insert logs, retrying", "err", err, "from", from, "to", to)
 			return err

core/chains/evm/logpoller/log_poller_test.go

@@ -965,8 +965,8 @@ func TestLogPoller_PollAndSaveLogs(t *testing.T) {
 			lgs, err = th.ORM.SelectLogsByBlockRange(11, 17)
 			require.NoError(t, err)
 			assert.Equal(t, 7, len(lgs))
-			th.assertHaveCanonical(t, 15, 16)
-			th.assertDontHave(t, 11, 14) // Do not expect to save backfilled blocks.
+			th.assertHaveCanonical(t, 14, 16) // Should have last finalized block plus unfinalized blocks
+			th.assertDontHave(t, 11, 13)      // Should not have older finalized blocks
 
 			// Verify that a custom block timestamp will get written to db correctly also
 			b, err = th.Client.BlockByNumber(testutils.Context(t), nil)
@@ -1057,8 +1057,8 @@ func TestLogPoller_PollAndSaveLogsDeepReorg(t *testing.T) {
 			require.NoError(t, err)
 			assert.Equal(t, hexutil.MustDecode(`0x0000000000000000000000000000000000000000000000000000000000000002`), lgs[0].Data)
 			th.assertHaveCanonical(t, 1, 1)
-			th.assertDontHave(t, 2, 5) // These blocks are backfilled
-			th.assertHaveCanonical(t, 6, 10)
+			th.assertDontHave(t, 2, 3) // These blocks are backfilled
+			th.assertHaveCanonical(t, 5, 10)
 		})
 	}
 }