Use uvloop by default

[r4victor]

The PR installs uvicorn[standard], which includes uvloop and makes uvicorn use it by default when possible.

uvloop improves server performance 10-20% (throughput, latency), which is noticeable on fast endpoints:

without uv loop:

(venvt) ➜  stuff wrk http://localhost:8000/healthcheck
Running 10s test @ http://localhost:8000/healthcheck
  2 threads and 10 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency     9.61ms   26.02ms 223.25ms   93.55%
    Req/Sec     1.50k   433.86     1.95k    84.85%
  29731 requests in 10.02s, 4.11MB read
Requests/sec:   2966.66
Transfer/sec:    420.13KB

with uvloop:

(venvt) ➜  stuff wrk http://localhost:8000/healthcheck             
Running 10s test @ http://localhost:8000/healthcheck
  2 threads and 10 connections
  Thread Stats   Avg      Stdev     Max   +/- Stdev
    Latency    11.63ms   32.02ms 265.65ms   91.91%
    Req/Sec     1.84k   537.20     2.36k    84.74%
  35526 requests in 10.02s, 4.91MB read
Requests/sec:   3544.50
Transfer/sec:    501.97KB

As expected, there is no effect for slow API endpoints (e.g. /api/runs/list).