feat:`POL` token migration

[leovct]

Description

• [x] Implement a new migration script called 7_pol_migration.js, based on plasma-bridge-update branch, that:
  • [x] deploys POLToken and PolygonMigration,
  • [x] adds pol, matic and polygonMigration mapping to the Registry,
  • [x] mints POL to PolygonMigration,
  • [x] updates the implementation of the DepositManager,
  • [ ] migrates MATIC tokens to POL on L1.
• [ ] Add a script to test standard user bridge operations:
  • Bridge MATIC/POL on L1 and receive MATIC on L2.
  • Withdraw MATIC/POL on L2 and receive POL on L1.

Other minor stuff

• Move updateContractMap to utils to share implementation between scripts.

Jira Ticket

• DVT-1036

Test

• [ ] TODO