lotus-shed backfill events doesn't touch events_seen

[rvagg]

We forgot to update backfilling when we landed #12080. If you run backfill-events after that migration (1.28) then it's not going to update the table that we need to determine if we've processed that tipset.

We're going to nuke the lotus-shed backfilling, see conversation in #12330 and #12116, but for now it's still used and it should work.

We need to copy this logic:

lotus/chain/events/filter/index.go

Lines 870 to 879 in 6bdbbc0

	// this statement will mark the tipset as processed and will insert a new row if it doesn't exist
	// or update the reverted field to false if it does
	_, err = tx.Stmt(ei.stmtUpsertEventsSeen).Exec(
	te.msgTs.Height(),
	tsKeyCid.Bytes(),
	)
	if err != nil {
	return xerrors.Errorf("exec upsert events seen: %w", err)
	}

Into the bottom of this closure:

lotus/cmd/lotus-shed/indexes.go

Line 179 in 6bdbbc0

processHeight := func(ctx context.Context, cnt int, msgs []lapi.Message, receipts []*types.MessageReceipt) error {