Attempt to use the scalset API and caching

On github, attempt to use the scaleset API to list all runners without
pagination. This will avoid missing runners and accidentally removing them.

Fall back to paginated API if we can't use the scaleset API.

Add ability to retrieve all instances from cache, for an entity.

Signed-off-by: Gabriel Adrian Samfira <gsamfira@cloudbasesolutions.com>

cache/instance_cache.go

@@ -98,6 +98,22 @@ func (i *InstanceCache) GetInstancesForScaleSet(scaleSetID uint) []params.Instan
 	return filteredInstances
 }
 
+func (i *InstanceCache) GetEntityInstances(entityID string) []params.Instance {
+	pools := GetEntityPools(entityID)
+	poolsAsMap := map[string]bool{}
+	for _, pool := range pools {
+		poolsAsMap[pool.ID] = true
+	}
+
+	ret := []params.Instance{}
+	for _, val := range i.GetAllInstances() {
+		if _, ok := poolsAsMap[val.PoolID]; ok {
+			ret = append(ret, val)
+		}
+	}
+	return ret
+}
+
 func SetInstanceCache(instance params.Instance) {
 	instanceCache.SetInstance(instance)
 }
@@ -121,3 +137,7 @@ func GetInstancesForPool(poolID string) []params.Instance {
 func GetInstancesForScaleSet(scaleSetID uint) []params.Instance {
 	return instanceCache.GetInstancesForScaleSet(scaleSetID)
 }
+
+func GetEntityInstances(entityID string) []params.Instance {
+	return instanceCache.GetEntityInstances(entityID)
+}