* SecureBackupPanel: replace `isKeyBackupTrusted`
`MatrixClient.isKeyBackupTrusted` -> `CryptoApi.isKeyBackupTrusted`
* SecureBackupPanel: replace `getKeyBackupEnabled`
`MatrixClient.getKeyBackupEnabled` -> `CryptoApi.getActiveSessionBackupVersion`
* SecureBackupPanel: replace `deleteKeyBackupVersion`
`MatrixClient.deleteKeyBackupVersion` -> `CryptoApi.deleteKeyBackupVersion`
* Do not show session count if we have no info
We shouldn't say "zero sessions to back up" if we don't know.
* SecureBackupPanel: distinguish between server and active backup
11f258e62e