adds containerd-shim-lcow-v2 shim (#2627)

In this commit, we are adding the initial draft of `containerd-shim-lcow-v2`. This shim is used for running Linux Containers on Windows.

As part of this commit, we are adding the following-
- The main entrypoint and supporting logic to start + serve the shim server.
- The stubs for Task Service and Shimdiag service.
- The implementation for `Sandbox` service.
- The implementation for `VM Controller` which manages the VM lifecycle and operations.

Signed-off-by: Harsh Rawat <harshrawat@microsoft.com>

Author: rawahars

cmd/containerd-shim-lcow-v2/containerd-shim-lcow-v2.exe.manifest

@@ -0,0 +1,17 @@
+<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
+<assembly xmlns="urn:schemas-microsoft-com:asm.v1" manifestVersion="1.0">
+    <description>containerd-shim-lcow-v2</description>
+    <compatibility xmlns="urn:schemas-microsoft-com:compatibility.v1">
+        <application>
+            <!-- Windows 10+, Windows 11, Server 2016/2019/2022/2025 and future -->
+            <supportedOS Id="{8e0f7a12-bfb3-4fe8-b9a5-48fd50a15a9a}"/>
+        </application>
+    </compatibility>
+    <application xmlns="urn:schemas-microsoft-com:asm.v3">
+        <!-- Long Path Enablement -->
+        <windowsSettings xmlns:ws2="http://schemas.microsoft.com/SMI/2016/WindowsSettings">
+            <ws2:longPathAware>true</ws2:longPathAware>
+        </windowsSettings>
+    </application>
+</assembly>
+

cmd/containerd-shim-lcow-v2/main.go

@@ -0,0 +1,93 @@
+//go:build windows
+
+// containerd-shim-lcow-v2 is a containerd shim implementation for Linux Containers on Windows (LCOW).
+package main
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"io"
+	"os"
+
+	"github.com/Microsoft/hcsshim/cmd/containerd-shim-lcow-v2/service"
+	_ "github.com/Microsoft/hcsshim/cmd/containerd-shim-lcow-v2/service/plugin"
+	runhcsopts "github.com/Microsoft/hcsshim/cmd/containerd-shim-runhcs-v1/options"
+	"github.com/Microsoft/hcsshim/internal/log"
+	"github.com/Microsoft/hcsshim/internal/oc"
+	"github.com/Microsoft/hcsshim/internal/shim"
+
+	"github.com/containerd/errdefs"
+	"github.com/sirupsen/logrus"
+	"go.opencensus.io/trace"
+)
+
+// Add a manifest to get proper Windows version detection.
+//go:generate go tool github.com/josephspurrier/goversioninfo/cmd/goversioninfo -platform-specific
+
+func main() {
+	logrus.AddHook(log.NewHook())
+
+	// Register our OpenCensus logrus exporter so that trace spans are emitted via logrus.
+	trace.ApplyConfig(trace.Config{DefaultSampler: oc.DefaultSampler})
+	trace.RegisterExporter(&oc.LogrusExporter{})
+
+	logrus.SetFormatter(log.NopFormatter{})
+	logrus.SetOutput(io.Discard)
+
+	// Set the log configuration.
+	// If we encounter an error, we exit with non-zero code.
+	if err := setLogConfiguration(); err != nil {
+		_, _ = fmt.Fprintf(os.Stderr, "%s: %s", service.ShimName, err)
+		os.Exit(1)
+	}
+
+	// Start the shim manager event loop. The manager is responsible for
+	// handling containerd start/stop lifecycle calls for the shim process.
+	shim.Run(context.Background(), newShimManager(service.ShimName), func(c *shim.Config) {
+		// We don't want the shim package to set up logging options.
+		c.NoSetupLogger = true
+	})
+}
+
+// setLogConfiguration reads the runtime options from stdin and sets the log configuration.
+// We only set up the log configuration for serve action.
+func setLogConfiguration() error {
+	// We set up the log configuration in the serve action only.
+	// This is because we want to avoid reading the stdin in start action,
+	// so that we can pass it along to the invocation for serve action.
+	if len(os.Args) > 1 && os.Args[len(os.Args)-1] == "serve" {
+		// The serve process is started with stderr pointing to panic.log file.
+		// We want to keep that file only for pure Go panics. Any explicit writes
+		// to os.Stderr should go to stdout instead, which is connected to the parent's
+		// stderr for regular logging.
+		// We can safely redirect os.Stderr to os.Stdout because in case of panics,
+		// the Go runtime will write the panic stack trace directly to the file descriptor,
+		// bypassing os.Stderr, so it will still go to panic.log.
+		os.Stderr = os.Stdout
+
+		opts, err := shim.ReadRuntimeOptions[*runhcsopts.Options](os.Stdin)
+		if err != nil {
+			if !errors.Is(err, errdefs.ErrNotFound) {
+				return fmt.Errorf("failed to read runtime options from stdin: %w", err)
+			}
+		}
+
+		if opts != nil {
+			if opts.LogLevel != "" {
+				// If log level is specified, set the corresponding logrus logging level.
+				lvl, err := logrus.ParseLevel(opts.LogLevel)
+				if err != nil {
+					return fmt.Errorf("failed to parse shim log level %q: %w", opts.LogLevel, err)
+				}
+				logrus.SetLevel(lvl)
+			}
+
+			if opts.ScrubLogs {
+				log.SetScrubbing(true)
+			}
+		}
+		_ = os.Stdin.Close()
+	}
+	return nil
+}