Migrate pallet-sudo to pallet!

[ascjones]

Part of #7882.

Converts the Sudo pallet to the new pallet attribute macro introduced in #6877.

Following the upgrade guidelines here: https://crates.parity.io/frame_support/attr.pallet.html#upgrade-guidelines.

⚠️ Breaking Change ⚠️

From https://crates.parity.io/frame_support/attr.pallet.html#checking-upgrade-guidelines

storages now use PalletInfo for module_prefix instead of the one given to decl_storage: Thus any use of this pallet in construct_runtime! should be careful to update name in order not to break storage or to upgrade storage (moreover for instantiable pallet). If pallet is published, make sure to warn about this breaking change.

So users of the Sudo pallet must be careful about the name they used in construct_runtime!. Hence the runtime-migration label, which might not be needed depending on the configuration of the Sudo pallet.

[gui1117]

polkadot doesn't needs migration as not used in polkadot/kusama and westend has unchanged pallet prefix.

[ascjones]

CI is failing with this warning as error https://gitlab.parity.io/parity/substrate/-/jobs/867537#L473:

error: associated function is never used: `call_functions`
  --> frame/sudo/src/mock.rs:48:12
   |
48 |     #[pallet::call]
   |       ^^^^

I don't get it because it is clearly used by the construct_runtime! expansion: FnEncode ( logger :: Pallet :: < Test > :: call_functions. Any ideas @thiolliere?

[gui1117]

yes but the metadata function (which uses call_functions) generated by construct_runtime is unused I guess, thus it complains about unused items.

[ascjones]

Ah yeah, I wonder how that worked with the legacy decl_module! though

[gui1117]

maybe rustc is not doing the same checks for both macros kind.
Anyway you can add a dummy test:

#[test] 
fn dummy_use() {
Test::metadata();
}

Or actually we can add in construct_runtime #[allow_unused] for the function metadata.

[ascjones]

Ah yeah, I wonder how that worked with the legacy decl_module! though

The original macro already annotated the generated fn with #[allow(dead_code)], I've just done the same for the new one.