Cleanup Immutable File in Cardano transaction

[jpraynaud]

Why

We need to remove all the code related to the immutable files for the Cardano transaction which is not used anymore since we transitioned to chain sync.

What

Clean the code form the immutable files in the Cardano transaction and simplify it where possible.

How

• Create a migration to remove the immutable file number in cardano_tx table (signer and aggregator)
• Clean the immutable files from the cardano_block_scanner module of mithril-common
  • Remove the immutable_block_streamer sub module
  • Remove the ImmutableLowerBoundFinder
  • Remove the CardanoImmutableBlockScanner
  • Remove all the references to ImmutableFileNumber in the module
  • Remove the dir_path parameter from BlockScanner::scan
• Clean the integration tests