Sync backwards based on last certificate

[ishantiw]

Description

When chain connector plugins starts loading it checks for lastCertificate and associated data to create a ccu transaction. We need to pull missing data based on the lastCertificate block header.

Acceptance Criteria

• Should pass all the related tests

[ishantiw]

Since we cannot get the correct outboxRootWitness if we sync backwards this is why we don't need this feature. A node needs to have enabled chain connector plugin in order to retrieve all the relevant data to create a CCU transaction.