Update FFTM generic components to work with connectors that do not have detailed block information

[Chengxuan]

As part of hyperledger-firefly/evmconnect#191, we introduced a mode in which the connector can run in a mode that only tracks the head block number without downloading any block information (therefore, not building a canonical chain).

Therefore, the following generic components that use the block information need to be updated to cope with the new mode:

• confirmation manager
• block listener