[utils] Add a Unicode data generator util package (#39213)

* Add a Unicode data generator util package

* Add a common GenUtils library

* Use string methods for reading/writing files

utils/gen-unicode-data/Sources/GenUtils/BitArray.swift

@@ -0,0 +1,41 @@
+//===----------------------------------------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2021 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+public struct BitArray {
+  public var words: [UInt64]
+  public var size: UInt16
+  
+  public init(size: Int) {
+    self.words = .init(repeating: 0, count: (size + 63) / 64)
+    self.size = UInt16(size)
+  }
+  
+  public subscript(_ bit: Int) -> Bool {
+    get {
+      return words[bit / 64] & (1 << (bit % 64)) != 0
+    }
+    
+    set {
+      if newValue {
+        words[bit / 64] |= 1 << (bit % 64)
+      } else {
+        words[bit / 64] &= ~(1 << (bit % 64))
+      }
+    }
+  }
+  
+  public mutating func insert(_ bit: Int) -> Bool {
+    let oldData = words[bit / 64]
+    words[bit / 64] |= 1 << (bit % 64)
+    return oldData & (1 << (bit % 64)) == 0
+  }
+}