[Backtracing][Linux] Add Linux support to the _Backtracing module.

Use the new module structure rather the old SwiftShims header.  This
is much cleaner and lets us include operating system headers to get
the relevant definitions where possible.

Add code to support ELF and DWARF, including decompression using
zlib, zstd and liblzma if those turn out to be required and available.

rdar://110261712

Author: al45tair

include/swift/Runtime/Backtrace.h

@@ -134,7 +134,8 @@ struct BacktraceSettings {
 
 SWIFT_RUNTIME_STDLIB_INTERNAL BacktraceSettings _swift_backtraceSettings;
 
-SWIFT_RUNTIME_STDLIB_SPI SWIFT_CC(swift) bool _swift_isThunkFunction(const char *mangledName);
+SWIFT_RUNTIME_STDLIB_SPI
+bool _swift_backtrace_isThunkFunction(const char *mangledName);
 
 SWIFT_RUNTIME_STDLIB_SPI
 char *_swift_backtrace_demangle(const char *mangledName,

stdlib/public/Backtracing/ArrayImageSource.swift

@@ -0,0 +1,50 @@
+//===--- ArrayImageSource.swift - An image source backed by an Array -------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2023 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
+//
+//===----------------------------------------------------------------------===//
+//
+// Defines ArrayImageSource, an image source that is backed by a Swift Array.
+//
+//===----------------------------------------------------------------------===//
+
+import Swift
+
+@_implementationOnly import OS.Libc
+
+enum ArrayImageSourceError: Error {
+  case outOfBoundsRead(UInt64, UInt64)
+}
+
+struct ArrayImageSource<T>: ImageSource {
+  private var array: Array<T>
+
+  public init(array: Array<T>) {
+    self.array = array
+  }
+
+  public var isMappedImage: Bool { return false }
+  public var path: String? { return nil }
+  public var bounds: Bounds? {
+    return Bounds(base: 0, size: Size(array.count * MemoryLayout<T>.stride))
+  }
+
+  public func fetch<U>(from addr: Address,
+                       into buffer: UnsafeMutableBufferPointer<U>) throws {
+    try array.withUnsafeBytes{
+      let size = Size($0.count)
+      let requested = Size(buffer.count * MemoryLayout<U>.stride)
+      if addr > size || requested > size - addr {
+        throw ArrayImageSourceError.outOfBoundsRead(addr, requested)
+      }
+
+      memcpy(buffer.baseAddress!, $0.baseAddress! + Int(addr), Int(requested))
+    }
+  }
+}