[Frigate] Display Coral EdgeTPU FPS and load stats in system metrics view

**Describe what you are trying to accomplish and why in non technical terms** It is very useful and easy-and-simple to implement stats of processing FPS and device load for Coral edgetpu in system metrics view because these 2 parameters came from inherence time. This will alow to monitor free processing capacity of Coral edgetpu. As you see from code bellow it counts frames from all cameras handled by specific Coral module. These additional stats are very useful for load balancing, information and debugging Also AI is added as bonus information max FPS for used model :) **Describe the solution you'd like** I want in addition to inference time to see in system metrics screen, stats for load of Coral as well how many fps it processes **Describe alternatives you've considered** A clear and concise description of any alternative solutions or features you've considered. **Additional context** Here is AI generated code for direct integration in GeneralMetrics.tsx, with helpful code comm