Add stat RPC (#614)

Add `Stat` RPC to vminitd.

`Stat` RPC is used to stat file system objects in the VM. It accepts the
path to the object (resolved against VM root) and returns the stat
result.

Sources/ContainerizationOS/Stat.swift

@@ -0,0 +1,88 @@
+//===----------------------------------------------------------------------===//
+// Copyright © 2026 Apple Inc. and the Containerization project authors.
+//
+// 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
+//
+//   https://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.
+//===----------------------------------------------------------------------===//
+
+/// A timestamp with second and nanosecond precision.
+public struct TimeSpec: Sendable, Hashable {
+    /// Seconds since the Unix epoch.
+    public var seconds: Int64
+    /// Nanoseconds past the second.
+    public var nanoseconds: Int32
+
+    public init(seconds: Int64, nanoseconds: Int32) {
+        self.seconds = seconds
+        self.nanoseconds = nanoseconds
+    }
+}
+
+/// File metadata returned by a `stat` call.
+public struct Stat: Sendable, Hashable {
+    /// ID of device containing file (`st_dev`).
+    public var dev: UInt64
+    /// Inode number (`st_ino`).
+    public var ino: UInt64
+    /// File type and mode (`st_mode`).
+    public var mode: UInt32
+    /// Number of hard links (`st_nlink`).
+    public var nlink: UInt64
+    /// User ID of owner (`st_uid`).
+    public var uid: UInt32
+    /// Group ID of owner (`st_gid`).
+    public var gid: UInt32
+    /// Device ID, if special file (`st_rdev`).
+    public var rdev: UInt64
+    /// Total size in bytes (`st_size`).
+    public var size: Int64
+    /// Preferred I/O block size (`st_blksize`).
+    public var blksize: Int64
+    /// Number of 512-byte blocks allocated (`st_blocks`).
+    public var blocks: Int64
+    /// Time of last access (`st_atim`).
+    public var atime: TimeSpec
+    /// Time of last modification (`st_mtim`).
+    public var mtime: TimeSpec
+    /// Time of last status change (`st_ctim`).
+    public var ctime: TimeSpec
+
+    public init(
+        dev: UInt64,
+        ino: UInt64,
+        mode: UInt32,
+        nlink: UInt64,
+        uid: UInt32,
+        gid: UInt32,
+        rdev: UInt64,
+        size: Int64,
+        blksize: Int64,
+        blocks: Int64,
+        atime: TimeSpec,
+        mtime: TimeSpec,
+        ctime: TimeSpec
+    ) {
+        self.dev = dev
+        self.ino = ino
+        self.mode = mode
+        self.nlink = nlink
+        self.uid = uid
+        self.gid = gid
+        self.rdev = rdev
+        self.size = size
+        self.blksize = blksize
+        self.blocks = blocks
+        self.atime = atime
+        self.mtime = mtime
+        self.ctime = ctime
+    }
+}