Fix support for API concurrency > 1 by updating Uvicorn launch logic

[DifferentialityDevelopment]

Fix for the bug when launching the serverless worker locally with api concurrency > 1

I got the following error:
WARNING: You must pass the application as an import string to enable 'reload' or 'workers'.

As per my issue I created here
#407

[DifferentialityDevelopment]

I notice that running with concurrency is totally not a thing on Windows..
I was able to get it "working" on linux with the above changes
But it requires I give it test input data else the workers just exit immediately, if I just use concurrency = 1 then the worker persists.

I was going through all this to be able to stress test my application and gather data on per request memory usage, peak memory usage with different concurrency levels etc
Does concurrency_modifier even have any effect in development environment if testing with concurrency = 1
My worker handler itself is async