Handle L1 Chain Reorganizaion

[jacque006]

What's wrong

Currently, our syncing node (and in the future packing/proposer node) do not handle chain reorganizations (old doc/link). This will cause issues with maintaining proper L2 state for deposits, pubkeys, rollups, etc.

How we can fix it

TODO Discuss once project is further along. Likely will need to drop parts of local/db state and re-sync from events on L1.

Example of how to test in test suite: https://github.com/hermeznetwork/hermez-node/blob/f4f77aa84bd8a55fdc057fde6de9d60fac9173b7/db/l2db/l2db_test.go#L501