It looks like driver 525 (aka, cuda driver 12.0) has problems with the cuda v12 library
we compile against, so run v11 on those older drivers if detected.
This change adds support for multiple concurrent requests, as well as
loading multiple models by spawning multiple runners. The default
settings are currently set at 1 concurrent request per model and only 1
loaded model at a time, but these can be adjusted by setting
OLLAMA_NUM_PARALLEL and OLLAMA_MAX_LOADED_MODELS.