dev: Add orml_asset_registry

[NunoAlexandre]

Part 1/2 of #825

development

• Add orml-asset-registry pallet to dependencies
• Add orml_asset_registry pallet to the development runtime
• Try and use CurrencyId as the AssetId type of this pallet
• Implement mock AssetProcessor
• Add CurrencyId::ForeignAsset variant
• Test that we can register the native as well as new foreign asset tokens
• Adapt the XCM config to make use of this registry

general

• Extend dependency to allow for origin checks based on the asset id
  asset-registry: Pass Asset Id to AuthorityOrigin open-web3-stack/open-runtime-module-library#762
• Extend orml to allow for AssetRegistry to be passed as a trait to pools later on
  asset-registry: And and Implement Inspect + Mutate traits open-web3-stack/open-runtime-module-library#767
• Drop our custom TokenMetadata trait
  See commit description
• Define CustomMetadata
  See dev: Add orml_asset_registry #829 (comment)
• Drop CurrencyId::Permissioned
• Fine tune values and configs (see the comments I left on my self-review)

[NunoAlexandre]

Important notes for reviewers 👇

[NunoAlexandre]

@mikiquantum @offerijns please have a careful look at this. Check the todo list in the PR description and at the comments I left in my self-review with callouts to specific changes where your take is specially important.

[NunoAlexandre]

Reviews, please have a look 👇

[hieronx]

This looks really good! Will be much more manageable than the current setup 🔥

[NunoAlexandre]

@offerijns thanks for the review! I have addressed the loose ends and have dried two shared implementations cross-runtimes but no semantics changed have taken place since your last review. Can you have another look?

[mikiquantum]

Overall looks good, I have a few questions, forgive me if I am late to the party on those.

I think EnsureRootOr<HalfOfCouncil> is fine.

🙏

[NunoAlexandre]

We need to add this here because we need the runtime-benchmarks flag to be available for runtime-common