Implement Storage trait

Чтобы инстанс мог восстановиться после рестарта, мало заперсистить raft_log (#10 (closed)), надо ещё уметь его вычитывать.

mentioned in commit 48b4b331

By Yaroslav Dynnikov on 2021-12-24T14:42:35 (imported from GitLab)

assigned to @rosik

By Yaroslav Dynnikov on 2021-12-24T14:43:14 (imported from GitLab)

added 1 deleted label

removed 1 deleted label

mentioned in issue #985 (closed)

mentioned in commit a4f577c0

mentioned in commit 9c117a0a

mentioned in commit dbc74da6

mentioned in commit 2f213ea2

mentioned in commit 5619d61d

mentioned in commit 0154f6ab

mentioned in commit b6233d25