Improve Dictionary and Enumerable Python Handling

Expected Behavior

• Error messages are informative and helpful
• Minimize the pure C# types in Python, and when absolutely required extend with common interface methods (len, items, keys)

Actual Behavior

markets = qb.BrokerageModel.DefaultMarketMap
<System.Collections.ObjectModel.ReadOnlyDictionary...

bars = qb.History[TradeBar](ibm.Symbol, start, end, Resolution.Minute)
<QuantConnect.Util.MemoizingEnumerable[TradeBar] object at 0x7...

Potential Solution

1. Make the method return a naitve python type if possible -- in PythonNet if required.
2. If not possible; provide common APIs for each one. len, append, items, keys etc.
3. Catch the Memoizing enumerable / readonly dictionary error messages and provide a more informative error message.

Reproducing the Problem

Python History API Calls

Checklist

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• I have confirmed that this issue exists on the current master branch
• I have confirmed that this is not a duplicate issue by searching issues

• I have provided detailed steps to reproduce the issue

Start with the Python History API calls and the returned ReadOnlyDictionary and MemoizingEnumerable examples described in the issue. Determine whether PythonNet can provide native Python types or whether common methods and clearer error messages are required. Done means Python callers receive usable collection behavior and informative errors.