Adding migrations to clean Rococo Gov 1 storage & reserved funds (#1849)

Following
[polkadot#7314](https://github.com/paritytech/polkadot/pull/7314) and
after merging https://github.com/paritytech/polkadot-sdk/pull/1177 this
PR solves https://github.com/paritytech/polkadot-sdk/issues/1618

The following is a summary of the outcome of the migration.

| Module | Total Accounts | Total stake to unlock | Total deposit to
unreserve |
| ------- | --------------- | --------------------- |
-------------------------- |
| Elections Phragmen | 27 | 1,132.821063320441 ROC | 1.465386531600 ROC
|
| Democracy | 69 | 2733.923509345613 ROC | 0.166666665000 ROC |
| Tips | 4 | N/A | 0.015099999849 ROC |

The migrations will also remove the following amount of keys

103 Democracy keys 🧹
5 Council keys 🧹
1 TechnicalCommittee keys 🧹
25 PhragmenElection keys 🧹
1 TechnicalMembership keys 🧹
9 Tips keys 🧹