spiderpig-apiserver: Invoke uvicorn directly
scap spiderpig-apiserver used to run fastapi run or fastapi dev
depending on the --dev flag. fastapi then called into uvicorn.
Since fastapi was updated in !956 (merged), its behavior has changed such that
it cannot be run as a background process in a terminal. To work
around that, I've changed scap spiderpig-apiserver to invoke
uvicorn directly.