Basics: remove AsyncFileSystem as unused (#6436)

Since `FileSystem` is now `Sendable`, we no longer need to keep `AsyncFileSystem`, which served only as a workaround for non-sendability. It wasn't non-blocking under the hood anyway, and a blocking FS I/O API would have to be designed from scratch anyway, not as a wrapper for the existing blocking APIs.

`AsyncFileSystem` actor declaration and its uses were removed. `FileSystem` can be used directly in our async code instead.

Author: MaxDesiatov

Sources/Basics/CMakeLists.txt

@@ -25,7 +25,6 @@ add_library(Basics
   DispatchTimeInterval+Extensions.swift
   EnvironmentVariables.swift
   Errors.swift
-  FileSystem/AsyncFileSystem.swift
   FileSystem/FileSystem+Extensions.swift
   FileSystem/Path+Extensions.swift
   FileSystem/TemporaryFile.swift

Sources/Basics/FileSystem/AsyncFileSystem.swift

@@ -52,7 +52,7 @@ public struct HTTPClientRequest: Sendable {
         url: URL,
         headers: HTTPClientHeaders = .init(),
         options: Options = .init(),
-        fileSystem: AsyncFileSystem,
+        fileSystem: FileSystem,
         destination: AbsolutePath
     ) -> Self {
         self.init(
@@ -75,7 +75,7 @@ public struct HTTPClientRequest: Sendable {
 
     public enum Kind: Sendable {
         case generic(HTTPMethod)
-        case download(fileSystem: AsyncFileSystem, destination: AbsolutePath)
+        case download(fileSystem: FileSystem, destination: AbsolutePath)
     }
 
     public struct Options: Sendable {