Fixes https://github.com/paritytech/polkadot-sdk/issues/4206

In #1340 one of the storage types was changed from `Candidates` to
`CandidateList`. Since the actual key includes the hash of this value,
all of the candidates stored here are (a) "missing" and (b) unable to
unreserve their candidacy bond.

This migration kills the storage values and refunds the deposit held for
each candidate.

---------

Signed-off-by: georgepisaltu <[email protected]>
Co-authored-by: georgepisaltu <[email protected]>
Co-authored-by: Oliver Tale-Yazdi <[email protected]>
Co-authored-by: georgepisaltu <[email protected]>

Part of #3326 

@ggwpez @Kianenigma @shawntabrizi



polkadot address: 12poSUQPtcF1HUPQGY3zZu2P8emuW9YnsPduA4XG3oCEfJVp

---------

Signed-off-by: Matteo Muraca <[email protected]>

Closes https://github.com/paritytech/polkadot-sdk-docs/issues/55

- Changes 'current storage version' terminology to less ambiguous
'in-code storage version' (suggestion by @ggwpez

)
- Adds a new example pallet `pallet-example-single-block-migrations`
- Adds a new reference doc to replace
https://docs.substrate.io/maintain/runtime-upgrades/ (temporarily living
in the pallet while we wait for developer hub PR to merge)
- Adds documentation for the `storage_alias` macro
- Improves `trait Hooks` docs 
- Improves `trait GetStorageVersion` docs
- Update the suggested patterns for using `VersionedMigration`, so that
version unchecked migrations are never exported
- Prevents accidental usage of version unchecked migrations in runtimes

https://github.com/paritytech/substrate/pull/14421#discussion_r1255467895
- Unversioned migration code is kept inside `mod version_unchecked`,
versioned code is kept in `pub mod versioned`
- It is necessary to use modules to limit visibility because the inner
migration must be `pub`. See
https://github.com/rust-lang/rust/issues/30905 and

https://internals.rust-lang.org/t/lang-team-minutes-private-in-public-rules/4504/40
for more.

### todo

- [x] move to reference docs to proper place within sdk-docs (now that
https://github.com/paritytech/polkadot-sdk/pull/2102 is merged)
- [x] prdoc

---------

Co-authored-by: Kian Paimani <[email protected]>
Co-authored-by: Juan <[email protected]>
Co-authored-by: Oliver Tale-Yazdi <[email protected]>
Co-authored-by: command-bot <>
Co-authored-by: gupnik <[email protected]>

* Add missing Cumulus licenses

* Typo

* Add missing Substrate licenses

* Single job checking the sub-repos in steps

* Remove dates

* Remove dates

* Add missing (C)

* Update FRAME UI tests

Signed-off-by: Oliver Tale-Yazdi <[email protected]>

* Update more UI tests

Signed-off-by: Oliver Tale-Yazdi <[email protected]>

---------

Signed-off-by: Oliver Tale-Yazdi <[email protected]>
Co-authored-by: Oliver Tale-Yazdi <[email protected]>

* restructure macro related exports

* restructure macro related exports

* wip

* wip

* update cargo lock

* refactor RuntimeDebug on unincluded segment

* fmt

* Companion: restructure `benchmarking` macro related exports (#3039)

* wip

* wip

* restructure benchmarking macro related exports

* add cargo lock

---------

Co-authored-by: parity-processbot <>

* add add and remove invulnerable dispatchables

* add migration

* fix benchmarking code

* add weights

* add migration to runtimes

* clippy

* pass SafeCallFilter

* make try-runtime work

* typos

Co-authored-by: Ankan <[email protected]>

* better insert and added test

* fix try-runtime update

* Apply suggestions from code review

Co-authored-by: Bastian Köcher <[email protected]>

* Update pallets/collator-selection/src/migration.rs

* check events in test

* Update pallets/collator-selection/src/migration.rs

Co-authored-by: Kian Paimani <[email protected]>

* just dispatchresult

* only sp_std for try-runtime

---------

Co-authored-by: Ankan <[email protected]>
Co-authored-by: Bastian Köcher <[email protected]>
Co-authored-by: Kian Paimani <[email protected]>