Python: Filters for FunctionCallBehavior.EnableFunctions should be optional

[madsbolaris]

Today, the filters property is required, even if its empty (see below)

execution_settings.function_call_behavior = FunctionCallBehavior.EnableFunctions(auto_invoke=True, filters={})

I should be able to just write...

execution_settings.function_call_behavior = FunctionCallBehavior.EnableFunctions(auto_invoke=True)

[moonbox3]

We're moving to support FunctionChoiceBehavior (#6910) where the filters for each class method are optional. However, for existing functionality, and for those users who haven't migrated from FunctionCallBehavior -> FunctionChoiceBehavior we can make the update to make the default filters, if not passed, as an empty dict.

[moonbox3]

Closed as of #6910.