Consider transaction enhancing on separate thread

[HonzaR]

Is your feature request related to a problem? Please describe.

After discussion, we could consider running the transaction-enhancing sub-phase of the overall block synchronization on a separate thread.

Describe the solution you'd like

We could move the whole enhanceTransactionDetails function on a separate thread.

Alternatives you've considered

Additional context

Analyze further and test it then. Also, consider what should happen when the end of the block synchronization is reached. Should it wait for the remaining enhancement before claiming the synchronization is done?