VPU Support (#645)

## 📝 Description

**What does this PR do and why is this change necessary?**

Adds `AcceleratedDevices` to `Instnace.Stats` and `GET linode/types`
Also adds `NETINT Quadra T1U` Capability enum.

## ✔️ How to Test

**How do I run the relevant unit/integration tests?**

```
make fixtures ARGS="-run TestInstance_withVPU"
```

instances.go

@@ -72,11 +72,12 @@ type Instance struct {
 
 // InstanceSpec represents a linode spec
 type InstanceSpec struct {
-	Disk     int `json:"disk"`
-	Memory   int `json:"memory"`
-	VCPUs    int `json:"vcpus"`
-	Transfer int `json:"transfer"`
-	GPUs     int `json:"gpus"`
+	Disk               int `json:"disk"`
+	Memory             int `json:"memory"`
+	VCPUs              int `json:"vcpus"`
+	Transfer           int `json:"transfer"`
+	GPUs               int `json:"gpus"`
+	AcceleratedDevices int `json:"accelerated_devices"`
 }
 
 // InstanceAlert represents a metric alert

regions.go

@@ -22,6 +22,7 @@ const (
 	CapabilityVlans                  string = "Vlans"
 	CapabilityVPCs                   string = "VPCs"
 	CapabilityVPCsExtra              string = "VPCs Extra"
+	CapabilityQuadraT1UVPU           string = "NETINT Quadra T1U"
 	CapabilityMachineImages          string = "Machine Images"
 	CapabilityBareMetal              string = "Bare Metal"
 	CapabilityDBAAS                  string = "Managed Databases"