Add basic tests for sqlean extensions in extensions.rs(Update extensions.rs)

Add test functions for Sqlean extensions (vss0, math0, fuzzy0, stats0)

- Added tests to extensions.rs for the following Sqlean extensions:
  - vss0: Vector similarity search
  - math0: Mathematical functions (e.g., sin(PI / 2))
  - fuzzy0: String distance (e.g., Levenshtein distance)
  - stats0: Statistical operations (e.g., calculating averages)
  
- Tests include creating sample tables, executing relevant SQL queries, and verifying the functionality of each extension.

Author: ManakRaj-7

libsql-sqlite3/test/rust_suite/src/extensions.rs

@@ -11,8 +11,51 @@ fn test_sqlite_vss() {
     conn.execute("CREATE VIRTUAL TABLE IF NOT EXISTS vss_demo USING vss0(a(2))", ())
         .unwrap();
     conn.execute("INSERT INTO vss_demo(rowid, a) VALUES (1, '[1.0, 2.0]'), (2, '[2.0, 2.0]'), (3, '[3.0, 2.0]')", ()).unwrap();
-    conn.execute(
-        "SELECT rowid, distance FROM vss_demo WHERE vss_search(?, ?) LIMIT 3",
-        params![1.0, 2.0],
-    ).unwrap();
-}
+    
+    let mut stmt = conn.prepare("SELECT rowid, distance FROM vss_demo WHERE vss_search(?, ?) LIMIT 3").unwrap();
+    let mut rows = stmt.query(params![1.0, 2.0]).unwrap();
+    while let Some(row) = rows.next().unwrap() {
+        let rowid: i32 = row.get(0).unwrap();
+        let distance: f64 = row.get(1).unwrap();
+        println!("Row ID: {}, Distance: {}", rowid, distance);
+    }
+}
+
+#[test]
+fn test_sqlite_math() {
+    let conn = Connection::open_in_memory().unwrap();
+    unsafe {
+        let _guard = LoadExtensionGuard::new(&conn).unwrap();
+        conn.load_extension("src/math0", None).unwrap();
+    }
+    
+    let result: f64 = conn.query_row("SELECT sin(PI() / 2)", [], |row| row.get(0)).unwrap();
+    assert!((result - 1.0).abs() < 1e-9, "Expected sin(PI/2) to be close to 1.0");
+}
+
+#[test]
+fn test_sqlite_fuzzy() {
+    let conn = Connection::open_in_memory().unwrap();
+    unsafe {
+        let _guard = LoadExtensionGuard::new(&conn).unwrap();
+        conn.load_extension("src/fuzzy0", None).unwrap();
+    }
+    
+    let result: i32 = conn.query_row("SELECT levenshtein('kitten', 'sitting')", [], |row| row.get(0)).unwrap();
+    assert_eq!(result, 3, "Expected levenshtein distance between 'kitten' and 'sitting' to be 3");
+}
+
+#[test]
+fn test_sqlite_stats() {
+    let conn = Connection::open_in_memory().unwrap();
+    unsafe {
+        let _guard = LoadExtensionGuard::new(&conn).unwrap();
+        conn.load_extension("src/stats0", None).unwrap();
+    }
+    
+    conn.execute("CREATE TABLE data(value REAL)", ()).unwrap();
+    conn.execute("INSERT INTO data(value) VALUES (1.0), (2.0), (3.0), (4.0), (5.0)", ()).unwrap();
+    
+    let avg: f64 = conn.query_row("SELECT avg(value) FROM data", [], |row| row.get(0)).unwrap();
+    assert!((avg - 3.0).abs() < 1e-9, "Expected average of values 1.0 to 5.0 to be 3.0");
+}