This is the second step of improvements over keypairs/keycards/accounts.
- `SyncKeycardAction` protobuf removed
- `SyncKeypair` protobuf is used for syncing keycards state as well as for all
keycards related changes
- `last_update_clock` column removed from `keypairs` table cause as well as
for accounts, any keycard related change is actually a change made on a related
keypair, thus a keypair's clock keeps the clock of the last change
- `position` column added to `keypairs` table, needed to display keycards in
the same order accross devices
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