feat: staking v5 migrations

[weichweich]

• rename Total
• kill SelectedCandidates
• rename CollatorState
• rename CandidatePool
• run benchmarks

custom types

This PR introduces new custom JS-types which are required for compatibility with our SDK and the Polkadot Apps. Please use the following types to test the code with the Polkadot Apps:

JS-Types

{}

Checklist:

• I have verified that the code works
  • No panics! (checked arithmetic ops, no indexing array[3] use get(3), ...)
• I have verified that the code is easy to understand
  • If not, I have left a well-balanced amount of inline comments
• This PR does not introduce new custom types
  • If not, I have opened a companion PR with the type changes in the KILT types-definitions repository
• I have left the code in a better state
• I have documented the changes (where applicable)

[wischli]

Do we not want to switch to the "correct way" of using storage versions?

pallets/parachain-staking/src/lib.rs

/// The current storage version.
const STORAGE_VERSION: StorageVersion = StorageVersion::new(4);
...
#[pallet::storage_version(STORAGE_VERSION)]

Apart from that some minor questions. Overall it looks good.

[weichweich]

Do we not want to switch to the "correct way" of using storage versions?

pallets/parachain-staking/src/lib.rs

/// The current storage version.
const STORAGE_VERSION: StorageVersion = StorageVersion::new(4);
...
#[pallet::storage_version(STORAGE_VERSION)]

Apart from that some minor questions. Overall it looks good.

I wouldn't do that now

[wischli]

Thanks for resolving my questions/would's. LGTM!