Make use_latent in duckling plugin configurable from project configs

[raina-rudra]

Is your feature request related to a problem? Please describe.
In old architecture, we could pass latent_entities = true/false for each SLU independently, when creating the Input object. But with core slu service, this is not possible anymore.
Duckling picks this attribute of Input object to decide if we want to look for latent_entities or not, hence we need secondary way to pass this attribute.

Describe the solution you'd like
If we can make it so, that when declaring duckling_plugin in project_config repo of said SLU, we can pass activate_latent_entities as true/false, this problem can be fixed.

Describe alternatives you've considered
A clear and concise description of any alternative solutions or features you've considered.

Additional context
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