Refactor keystore

[kamilsa]

Update format of keystore:

• Remove prefixes gran, babe, lp2p and other prefixes, use same prefixes as in substrate's keystore
• Move libp2p key into the network folder
• Add processing of suffixes like //Alice
• Align folder structure with polkadot. For example for polkadot it should be:

polkadot-polkadot
└── chains
    └── polkadot
        ├── db
        ├── keystore
        └── network

Current structure is:

polkadot-kagome
└── polkadot
    └── keystore