Add integration tests for inofity limits

inotify exposes a /proc interface to limit kernel memory usage. If those
limits are set too low, inotify cannot add all watches. The integration
test verifies, that Inotify yields an error in that case.

Tests/InotifyIntegrationTests/Utilities/withLowInotifyWatchLimit.swift

@@ -0,0 +1,22 @@
+import Foundation
+
+func withInotifyWatchLimit(of limit: Int, _ body: () async throws -> Void) async throws {
+	let confPath = URL(filePath: "/proc/sys/fs/inotify")
+	let filenames = ["max_user_watches", "max_user_instances", "max_queued_events"]
+	var previousLimits: [String: String] = [:]
+
+	for filename in filenames {
+		let filePath = confPath.appending(path: filename)
+		let currentLimit = try String(contentsOf: filePath, encoding: .utf8)
+		previousLimits[filename] = currentLimit
+		try "\(limit)".write(to: filePath, atomically: false, encoding: .utf8)
+	}
+
+	try await body()
+
+	for filename in filenames {
+		let filePath = confPath.appending(path: filename)
+		guard let previousLimit = previousLimits[filename] else { continue }
+		try previousLimit.write(to: filePath, atomically: false, encoding: .utf8)
+	}
+}