release sdk-v0.12.0-polkadot-v0.9.42

[clangenb]

Name of release branch: sdk-v0.12.0-polkadot-v0.9.42

Tasks:

• Create release branches in pallets, and node
• Create release branch in worker
• Tag release branch v0.12.0

[brenzi]

wait for #1390 to be merged