Add support for historical data download with backtest node

[faysou]

Pull Request

Added possibility to request backtest data during a backtest using a LiveMarketDataClient adapter

• Add possibility to add LiveMarketDataClients to backtestnode
• Add possibility to query new historical data during a backtest (which can be future data from the point of view of a past backtest time point), using existing LiveMarketDataClients without any change to them
• Subscribed data can also be requested periodically with a duration parameter in order to avoid large data requests
• data_client.py has been updated so it's possible for tasks to run in a sync way during a backtest
• Subscription during backtests can be captured by the backtest engine and transformed into a request to LiveMarketDataClient in order to download the required data
• This downloaded data can then be saved to a catalog (the next PR improves the saving system in a catalog in order to handle arbritrary disjoint time ranges that may be created during the dynamic download of data)
• When a LiveMarketDataClient is registered for a venue, it can be used for requests but not for subscriptions, a default backtest market data client is used instead in this case

Type of change

• New feature (non-breaking change which adds functionality)

How has this change been tested?

Tested data requests from live market client using an included example that works with databento
databento_backtest_with_data_client.py