Implements verifier and code gen for swift (#6373)

Updates test cases on linux

Adhere to new protocol naming

Adds fuzzing

Adds documentation

Adds support for string unions

Updated fuzzer generated code

tests/FlatBuffers.Test.Swift/Package.swift

@@ -28,7 +28,9 @@ let package = Package(
     .package(url: "https://github.com/grpc/grpc-swift.git", from: "1.0.0"),
   ],
   targets: [
-    .target(name: "SwiftFlatBuffers"),
+    .target(
+      name: "SwiftFlatBuffers",
+      dependencies: ["FlatBuffers"]),
     .testTarget(
       name: "FlatBuffers.Test.SwiftTests",
       dependencies: ["FlatBuffers", "GRPC"]),