Add `childstate_getStorageEntries` RPC (#9459)

* Add storage query functions for multiple keys

fixes #9203

* Query all keys in one request and add more tests

* Make it compatible with stable release channel

* Update to new futures

* Update client/rpc/src/state/state_full.rs

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

* Update client/rpc/src/state/state_full.rs

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

* Update client/rpc/src/state/state_full.rs

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

* Update client/rpc/src/state/state_full.rs

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

* Update client/rpc/src/state/state_full.rs

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

* Update client/rpc/src/state/state_light.rs

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

* Update client/rpc/src/state/state_light.rs

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

* Satisfy borrowck

* Remove non-RPC `storage_entries` functions.

* Revert "Remove non-RPC `storage_entries` functions."

This reverts commit d840015c59ce865f879178594088c79082e8d151.

* Revert "Revert "Remove non-RPC `storage_entries` functions.""

This reverts commit 5813b439a4b467e022c627e3fe60cf2fa5520db4.

* Finally some formatting

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