Change to using gopsutil for cross-OS process ops

Instead of trying to write out own code to do basic process
operations (e.g. checking if a PID is still running in a multi-OS
friendly manner), use shirou/gopsutil, a multi-platform library
that should abstract all the complexity away. Unlike our previous
approach on Windows, this one should actually work.

Signed-off-by: Matt Heon <mheon@redhat.com>

vendor/github.com/tklauser/numcpus/numcpus_windows.go

@@ -0,0 +1,41 @@
+// Copyright 2022 Tobias Klauser
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package numcpus
+
+import "golang.org/x/sys/windows"
+
+func getConfigured() (int, error) {
+	return int(windows.GetActiveProcessorCount(windows.ALL_PROCESSOR_GROUPS)), nil
+}
+
+func getKernelMax() (int, error) {
+	return int(windows.GetMaximumProcessorCount(windows.ALL_PROCESSOR_GROUPS)), nil
+}
+
+func getOffline() (int, error) {
+	return 0, ErrNotSupported
+}
+
+func getOnline() (int, error) {
+	return int(windows.GetActiveProcessorCount(windows.ALL_PROCESSOR_GROUPS)), nil
+}
+
+func getPossible() (int, error) {
+	return int(windows.GetActiveProcessorCount(windows.ALL_PROCESSOR_GROUPS)), nil
+}
+
+func getPresent() (int, error) {
+	return int(windows.GetActiveProcessorCount(windows.ALL_PROCESSOR_GROUPS)), nil
+}