Add support for feature flags

This change adds a features config that allows
individual features to be toggled at a global level. Each feature can (by default)
be controlled by an environment variable.

The GDS, MOFED, NVSWITCH, and GDRCOPY features are examples of such features.

Signed-off-by: Evan Lezar <elezar@nvidia.com>

internal/config/config.go

@@ -63,6 +63,9 @@ type Config struct {
 	NVIDIACTKConfig                  CTKConfig          `toml:"nvidia-ctk"`
 	NVIDIAContainerRuntimeConfig     RuntimeConfig      `toml:"nvidia-container-runtime"`
 	NVIDIAContainerRuntimeHookConfig RuntimeHookConfig  `toml:"nvidia-container-runtime-hook"`
+
+	// Features allows for finer control over optional features.
+	Features features `toml:"features,omitempty"`
 }
 
 // GetConfigFilePath returns the path to the config file for the configured system