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.go

@@ -0,0 +1,75 @@
+// Copyright 2018-2022 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 provides information about the number of CPUs in the system.
+//
+// It gets the number of CPUs (online, offline, present, possible or kernel
+// maximum) on Linux, Darwin, FreeBSD, NetBSD, OpenBSD, DragonflyBSD,
+// Solaris/Illumos or Windows systems.
+//
+// On Linux, the information is retrieved by reading the corresponding CPU
+// topology files in /sys/devices/system/cpu.
+//
+// On BSD systems, the information is retrieved using the hw.ncpu and
+// hw.ncpuonline sysctls, if supported.
+//
+// On Windows systems, the information is retrieved using the
+// GetActiveProcessorCount and GetMaximumProcessorCount functions, respectively.
+//
+// Not all functions are supported on Darwin, FreeBSD, NetBSD, OpenBSD,
+// DragonflyBSD, Solaris/Illumos and Windows. ErrNotSupported is returned in
+// case a function is not supported on a particular platform.
+package numcpus
+
+import "errors"
+
+// ErrNotSupported is the error returned when the function is not supported.
+var ErrNotSupported = errors.New("function not supported")
+
+// GetConfigured returns the number of CPUs configured on the system. This
+// function should return the same value as `getconf _SC_NPROCESSORS_CONF` on a
+// unix system.
+func GetConfigured() (int, error) {
+	return getConfigured()
+}
+
+// GetKernelMax returns the maximum number of CPUs allowed by the kernel
+// configuration. This function is only supported on Linux and Windows systems.
+func GetKernelMax() (int, error) {
+	return getKernelMax()
+}
+
+// GetOffline returns the number of offline CPUs, i.e. CPUs that are not online
+// because they have been hotplugged off or exceed the limit of CPUs allowed by
+// the kernel configuration (see GetKernelMax). This function is only supported
+// on Linux systems.
+func GetOffline() (int, error) {
+	return getOffline()
+}
+
+// GetOnline returns the number of CPUs that are online and being scheduled.
+func GetOnline() (int, error) {
+	return getOnline()
+}
+
+// GetPossible returns the number of possible CPUs, i.e. CPUs that
+// have been allocated resources and can be brought online if they are present.
+func GetPossible() (int, error) {
+	return getPossible()
+}
+
+// GetPresent returns the number of CPUs present in the system.
+func GetPresent() (int, error) {
+	return getPresent()
+}