feat: Add ClearLeftmostSetBit new algorithm with Junit tests (#5702)

src/test/java/com/thealgorithms/bitmanipulation/ClearLeftmostSetBitTest.java

@@ -0,0 +1,16 @@
+package com.thealgorithms.bitmanipulation;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+import org.junit.jupiter.api.Test;
+
+public class ClearLeftmostSetBitTest {
+
+    @Test
+    public void testClearLeftmostSetBit() {
+        assertEquals(10, ClearLeftmostSetBit.clearLeftmostSetBit(26)); // 11010 -> 01010
+        assertEquals(0, ClearLeftmostSetBit.clearLeftmostSetBit(1)); // 1 -> 0
+        assertEquals(3, ClearLeftmostSetBit.clearLeftmostSetBit(7)); // 111 -> 011
+        assertEquals(2, ClearLeftmostSetBit.clearLeftmostSetBit(6)); // 0110 -> 0010
+    }
+}