Allow for customization of `NautobotAdapter` loading on a per-model basis

[Kircheneer]

Environment

• Nautobot version:
• nautobot-ssot version:

Proposed Functionality

Use Case

If I need some special filtering logic for a certain model, I want a hook where I can place that.

Implementation Idea

Pseudo code:

def load(self):
    for model_name in self.top_level:
        if hasattr(self, f"load_{model_name}"):
            getattr(self, f"load_{model_name}")()
        else:
             # Normal code
             pass