[SPARK-51510] Add SQL-file based SQLTests suite

### What changes were proposed in this pull request?

This PR aims to add `SQL-file` based `SQLTests` suite as a new test framework. For example,

- `pipesyntax.sql`
```sql
VALUES (0), (1) tab(col)
|> EXTEND col * 2 AS result
```

- `pipesyntax.sql.json`
```json
[["0","0"],["1","2"]]
```

### Why are the changes needed?

This framework helps us improve test coverage by adding SQL file and golden answer files.

### Does this PR introduce _any_ user-facing change?

No.

### How was this patch tested?

Manual test against `Apache Spark 4.0.0 RC2` and pass the CIs.

```
$ swift test --filter SQLTests
...
􀟈  Suite SQLTests started.
􀟈  Test runAll() started.
pipesyntax.sql
select.sql
􁁛  Test runAll() passed after 0.083 seconds.
􁁛  Suite SQLTests passed after 0.083 seconds.
􁁛  Test run with 1 test passed after 0.083 seconds.
```

### Was this patch authored or co-authored using generative AI tooling?

No.

Closes #18 from dongjoon-hyun/SPARK-51510.

Authored-by: Dongjoon Hyun <[email protected]>
Signed-off-by: Dongjoon Hyun <[email protected]>

Author: dongjoon-hyun

.github/.licenserc.yaml

@@ -16,5 +16,6 @@ header:
     - '.nojekyll'
     - 'Package.swift'
     - '**/*pb.swift'
+    - 'Tests/SparkConnectTests/Resources/queries/**'
 
   comment: on-failure

Package.swift

@@ -53,7 +53,10 @@ let package = Package(
     ),
     .testTarget(
       name: "SparkConnectTests",
-      dependencies: ["SparkConnect"]
+      dependencies: ["SparkConnect"],
+      resources: [
+        .copy("Resources/queries")
+      ]
     ),
   ]
 )

Tests/SparkConnectTests/Resources/queries/pipesyntax.sql

@@ -0,0 +1,2 @@
+VALUES (0), (1) tab(col)
+|> EXTEND col * 2 AS result

Tests/SparkConnectTests/Resources/queries/pipesyntax.sql.json

@@ -0,0 +1 @@
+[["0","0"],["1","2"]]

Tests/SparkConnectTests/Resources/queries/select.sql

@@ -0,0 +1 @@
+SELECT 1

Tests/SparkConnectTests/Resources/queries/select.sql.json

@@ -0,0 +1 @@
+[["1"]]

Tests/SparkConnectTests/SQLTests.swift

@@ -0,0 +1,48 @@
+//
+// Licensed to the Apache Software Foundation (ASF) under one
+// or more contributor license agreements.  See the NOTICE file
+// distributed with this work for additional information
+// regarding copyright ownership.  The ASF licenses this file
+// to you 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 Foundation
+import Testing
+
+@testable import SparkConnect
+
+/// A test suite for various SQL statements.
+struct SQLTests {
+  let fm = FileManager.default
+  let path = Bundle.module.path(forResource: "queries", ofType: "")!
+  let encoder = JSONEncoder()
+
+#if !os(Linux)
+  @Test
+  func runAll() async throws {
+    let spark = try await SparkSession.builder.getOrCreate()
+    for name in try! fm.contentsOfDirectory(atPath: path).sorted() {
+      guard name.hasSuffix(".sql") else { continue }
+      print(name)
+
+      let sql = try String(contentsOf: URL(fileURLWithPath: "\(path)/\(name)"), encoding: .utf8)
+      let jsonData = try encoder.encode(try await spark.sql(sql).collect())
+      let answer = String(data: jsonData, encoding: .utf8)!
+      let expected = try String(contentsOf: URL(fileURLWithPath: "\(path)/\(name).json"), encoding: .utf8)
+      #expect(answer == expected.trimmingCharacters(in: .whitespacesAndNewlines))
+    }
+    await spark.stop()
+  }
+#endif
+}