[wpilibj] AddressableLEDBuffer: Add methods for reading individual RGB values (#6333)

This avoids the allocation/GC overhead of returning a Color8 value.

Also add an indexed iterator forEach to loop over the entire buffer.

wpilibj/src/test/java/edu/wpi/first/wpilibj/AddressableLEDBufferTest.java

@@ -6,6 +6,7 @@ package edu.wpi.first.wpilibj;
 
 import static org.junit.jupiter.api.Assertions.assertAll;
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.fail;
 import static org.junit.jupiter.params.provider.Arguments.arguments;
 
 import edu.wpi.first.wpilibj.util.Color;
@@ -70,4 +71,73 @@ class AddressableLEDBufferTest {
     assertEquals(firstRedColor8Bit, buffer.getLED8Bit(2));
     assertEquals(firstBlueColor8Bit, buffer.getLED8Bit(3));
   }
+
+  @Test
+  void getRed() {
+    var buffer = new AddressableLEDBuffer(1);
+    buffer.setRGB(0, 127, 128, 129);
+    assertEquals(127, buffer.getRed(0));
+  }
+
+  @Test
+  void getGreen() {
+    var buffer = new AddressableLEDBuffer(1);
+    buffer.setRGB(0, 127, 128, 129);
+    assertEquals(128, buffer.getGreen(0));
+  }
+
+  @Test
+  void getBlue() {
+    var buffer = new AddressableLEDBuffer(1);
+    buffer.setRGB(0, 127, 128, 129);
+    assertEquals(129, buffer.getBlue(0));
+  }
+
+  @Test
+  void forEach() {
+    var buffer = new AddressableLEDBuffer(3);
+    buffer.setRGB(0, 1, 2, 3);
+    buffer.setRGB(1, 4, 5, 6);
+    buffer.setRGB(2, 7, 8, 9);
+
+    buffer.forEach(
+        (index, r, g, b) -> {
+          switch (index) {
+            case 0:
+              {
+                assertAll(
+                    () -> assertEquals(1, r, "red at index 0"),
+                    () -> assertEquals(2, g, "green at index 0"),
+                    () -> assertEquals(3, b, "blue at index 0"));
+              }
+              break;
+            case 1:
+              {
+                assertAll(
+                    () -> assertEquals(4, r, "red at index 1"),
+                    () -> assertEquals(5, g, "green at index 1"),
+                    () -> assertEquals(6, b, "blue at index 1"));
+              }
+              break;
+            case 2:
+              {
+                assertAll(
+                    () -> assertEquals(7, r, "red at index 2"),
+                    () -> assertEquals(8, g, "green at index 2"),
+                    () -> assertEquals(9, b, "blue at index 2"));
+              }
+              break;
+            default:
+              fail("Unexpected index " + index);
+              break;
+          }
+        });
+  }
+
+  @Test
+  void forEachOnEmptyBuffer() {
+    var buffer = new AddressableLEDBuffer(0);
+
+    buffer.forEach((i, r, g, b) -> fail("Iterator should not be called on an empty buffer"));
+  }
 }