feat(pallet-tfgrid): check storage state

[renauter]

Description

The goal of this PR is to provide a mechanism to be able to check if storage is consistent in pallet-tfgrid.

1. try-runtime

For this, we use the try-runtime tool that allows to run tests on storage from simulated environment.
Here is how such tool can be executed against devnet:

RUST_LOG=debug cargo run --release --features=try-runtime try-runtime --runtime target/release/wbuild/tfchain-runtime/tfchain_runtime.compact.wasm --chain chainspecs/main/chainSpecRaw.json on-runtime-upgrade live --uri ws://10.10.0.151:9944

2. CheckStorageState

Ideally it should be part of some CI flow (TBD) to validate a given storage version.

For each storage version, we should implement a CheckStorageState struct with the associated checks.
This implementation should be included in the migration module that corresponds to the storage version at the end of the migration.
Example for V17Struct version of pallet-tfgrid, implementation is included in v17 module:

pub struct CheckStorageState<T: Config>(PhantomData<T>);

impl<T: Config> OnRuntimeUpgrade for CheckStorageState<T> {
    #[cfg(feature = "try-runtime")]
    fn pre_upgrade() -> Result<Vec<u8>, &'static str> {
        info!("current pallet version: {:?}", PalletVersion::<T>::get());
        assert!(PalletVersion::<T>::get() == types::StorageVersion::V17Struct);

        check_pallet_tfgrid::<T>();

        Ok(vec![])
    }
}

It also should be added in runtime the migration type to be triggered by the try-runtime command above.
Make sure you take into account the ordering of the migration stack according to the simulated environment and its current storage version (i.e if current version is V16Struct, you should have migration from V16Struct to V17Struct just before CheckStorageState of V17Struct).

type Migrations = (
    pallet_tfgrid::migrations::v17::MigrationV16toV17<Runtime>,
    pallet_tfgrid::migrations::v17::CheckStorageState<Runtime>,
);

3. check_pallet_tfgrid()

The code related to a specific storage version should be included in the following function:

pub fn check_pallet_tfgrid<T: Config>() {
    ...
}

To avoid code redundancy we will try as much as possible to take advantage of check functions from previous storage versions.

Related Issues:

• Fixes Pallet TFGrid: storage state checking #846

Checklist:

• My commits follow this conventional commits guide.