Upgrade polkadot v1.18.0

Tasks:

• Upgrade SDK and Subxt
• Upgrade pallets
• Upgrade runtime
• Upgrade oracle
• Upgrade tests

Upgrade Notes:

• ring-vfr and arkworks are deprecated – no need to maintain our forks anymore. (Reminder: these forks were maintained to avoid pulling paritytech/polkadot-sdk in addition to duniter/polkadot-sdk to compile the project.)
• duniter-subxt deprecation. Subxt's substrate-compat has also been deprecated (changelog):
  The goal is for Subxt to be independent of the Polkadot SDK version. We can now deprecate our Subxt fork, rely on the official version branch, and minimize future upgrade work. (Reminder: this fork was maintained to avoid conflicts between sp_core/sp-runtime from crates.io and sp-core/sp-runtime from duniter/polkadot-sdk.)

Proposition:

• Archive the deprecated repositories in the Duniter GitHub organization to avoid any confusion after the upcoming runtime and client upgrades.