[Swift] Migrating benchmarks to a newer lib. (#8168)

* Adds Nativestructs pointer push into ByteBuffer

Updates benchmarks & cleanup

Adds native struct vector tests

* Address PR comments

* Add more benchmarks

* Some benchmark cleanup

* Return back to 1M structs

* Tweak Structs benchmark

* Moves swift Benchmarks folder from /tests to /benchmarks

---------

Co-authored-by: Joakim Hassila <jocke@ordo.one>

benchmarks/swift/Package.swift

@@ -0,0 +1,42 @@
+// swift-tools-version:5.8
+/*
+ * Copyright 2020 Google Inc. All rights reserved.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import PackageDescription
+
+let package = Package(
+  name: "benchmarks",
+  platforms: [
+    .macOS(.v13),
+  ],
+  dependencies: [
+    .package(path: "../.."),
+    .package(
+      url: "https://github.com/ordo-one/package-benchmark",
+      from: "1.12.0"),
+  ],
+  targets: [
+    .executableTarget(
+      name: "FlatbuffersBenchmarks",
+      dependencies: [
+        .product(name: "FlatBuffers", package: "flatbuffers"),
+        .product(name: "Benchmark", package: "package-benchmark"),
+      ],
+      path: "Benchmarks/FlatbuffersBenchmarks",
+      plugins: [
+        .plugin(name: "BenchmarkPlugin", package: "package-benchmark"),
+      ]),
+  ])