Refine default thread selection for NUMA systems (#7322)

Until we have full NUMA support, this adjusts the default thread selection
algorithm to count up the number of performance cores across all sockets.

discover/types.go

@@ -175,6 +175,11 @@ func (si SystemInfo) GetOptimalThreadCount() int {
 	if len(si.System.CPUs) == 0 {
 		return 0
 	}
-	// Allocate thread count matching the performance cores on a single socket
-	return si.System.CPUs[0].CoreCount - si.System.CPUs[0].EfficiencyCoreCount
+
+	coreCount := 0
+	for _, c := range si.System.CPUs {
+		coreCount += c.CoreCount - c.EfficiencyCoreCount
+	}
+
+	return coreCount
 }