Add a CPU utilization resource monitor for overload manager (#34713)

Commit Message: Add a CPU utilization resource monitor for overload
manager. i.e. this can be configured to reject requests once CPU Utilization reaches a certain brownout point.

Signed-off-by: Can Cecen <ccecen@netflix.com>

Mirrored from https://github.com/envoyproxy/envoy @ 4d121628c648d2f565b4e6651484036981051763

BUILD

@@ -311,6 +311,7 @@ proto_library(
         "//envoy/extensions/rbac/matchers/upstream_ip_port/v3:pkg",
         "//envoy/extensions/regex_engines/v3:pkg",
         "//envoy/extensions/request_id/uuid/v3:pkg",
+        "//envoy/extensions/resource_monitors/cpu_utilization/v3:pkg",
         "//envoy/extensions/resource_monitors/downstream_connections/v3:pkg",
         "//envoy/extensions/resource_monitors/fixed_heap/v3:pkg",
         "//envoy/extensions/resource_monitors/injected_resource/v3:pkg",

envoy/extensions/resource_monitors/cpu_utilization/v3/BUILD

@@ -0,0 +1,9 @@
+# DO NOT EDIT. This file is generated by tools/proto_format/proto_sync.py.
+
+load("@envoy_api//bazel:api_build_system.bzl", "api_proto_package")
+
+licenses(["notice"])  # Apache 2
+
+api_proto_package(
+    deps = ["@com_github_cncf_xds//udpa/annotations:pkg"],
+)

envoy/extensions/resource_monitors/cpu_utilization/v3/cpu_utilization.proto

@@ -0,0 +1,19 @@
+syntax = "proto3";
+
+package envoy.extensions.resource_monitors.cpu_utilization.v3;
+
+import "udpa/annotations/status.proto";
+
+option java_package = "io.envoyproxy.envoy.extensions.resource_monitors.cpu_utilization.v3";
+option java_outer_classname = "CpuUtilizationProto";
+option java_multiple_files = true;
+option go_package = "github.com/envoyproxy/go-control-plane/envoy/extensions/resource_monitors/cpu_utilization/v3;cpu_utilizationv3";
+option (udpa.annotations.file_status).package_version_status = ACTIVE;
+
+// [#protodoc-title: CPU utilization]
+// [#extension: envoy.resource_monitors.cpu_utilization]
+
+// The CPU utilization resource monitor reports the Envoy process the CPU Utilization of the entire host.
+// Today, this only works on Linux and is calculated using the stats in the /proc/stat file.
+message CpuUtilizationConfig {
+}

versioning/BUILD

@@ -250,6 +250,7 @@ proto_library(
         "//envoy/extensions/rbac/matchers/upstream_ip_port/v3:pkg",
         "//envoy/extensions/regex_engines/v3:pkg",
         "//envoy/extensions/request_id/uuid/v3:pkg",
+        "//envoy/extensions/resource_monitors/cpu_utilization/v3:pkg",
         "//envoy/extensions/resource_monitors/downstream_connections/v3:pkg",
         "//envoy/extensions/resource_monitors/fixed_heap/v3:pkg",
         "//envoy/extensions/resource_monitors/injected_resource/v3:pkg",