fix(polkadot): upgrade to v1.2.0

[renauter]

Description

From previous PR #905:

• Upgrade to Polkadot v1.2.0

  • update versions of clap and serde_json dependencies
  • add libp2p-identity dependency
  • add block_relay to sc_service::build_network()
  • pallet-smart-contract: use transfer_allow_death() instead of transfer()
  • add sp-genesis-builder dependency
  • implement sp_genesis_builder::GenesisBuilder<Block> for runtime

• Complete PR chore(polkadot): upgrade to v1.2.0 #905 by adding:

  • js client: use transferAllowDeath instead of transfer (see doc https://polkadot.js.org/docs/substrate/extrinsics/#balances)
  • go client: use transfer_allow_death() instead of transfer()

About transferAllowDeath vs transferKeepAlive
Some documentation on how account is reaped and can be reactivated
https://medium.com/we-are-talisman/existential-deposit-1d3585e2d4d0

Related Issues:

• Runtime: update to polkadot 1.2.0 #906

Checklist:

• My commits follow this conventional commits guide.

[sameh-farouk]

let's add the changes from the reverted commit here