[wpilib] Use reflection to load main class, remove main from templates (#8627)

#8626 needs to switch to using reflection to load the robot class. Do
that with this PR so it's separate.

Also, remove the duplicated main files from the template, and instead
fixup vscode to handle this properly.

wpilibj/src/main/java/org/wpilib/framework/RobotBase.java

@@ -4,8 +4,8 @@
 
 package org.wpilib.framework;
 
+import java.lang.reflect.Constructor;
 import java.util.concurrent.locks.ReentrantLock;
-import java.util.function.Supplier;
 import org.wpilib.driverstation.DriverStation;
 import org.wpilib.hardware.hal.HAL;
 import org.wpilib.hardware.hal.HALUtil;
@@ -285,13 +285,39 @@ public abstract class RobotBase implements AutoCloseable {
   private static RobotBase m_robotCopy;
   private static boolean m_suppressExitWarning;
 
+  private static <T extends RobotBase> T constructRobot(Class<T> robotClass) throws Throwable {
+    Constructor<?>[] constructors = robotClass.getConstructors();
+    Constructor<?> defaultConstructor = null;
+    for (Constructor<?> constructor : constructors) {
+      Class<?>[] paramTypes = constructor.getParameterTypes();
+      if (paramTypes.length == 0) {
+        if (defaultConstructor != null) {
+          throw new IllegalArgumentException(
+              "Multiple default constructors found in robot class " + robotClass.getName());
+        }
+        defaultConstructor = constructor;
+      }
+    }
+
+    T robot;
+
+    if (defaultConstructor != null) {
+      robot = robotClass.cast(defaultConstructor.newInstance());
+    } else {
+      throw new IllegalArgumentException(
+          "No valid constructor found in robot class " + robotClass.getName());
+    }
+
+    return robot;
+  }
+
   /** Run the robot main loop. */
-  private static <T extends RobotBase> void runRobot(Supplier<T> robotSupplier) {
+  private static <T extends RobotBase> void runRobot(Class<T> robotClass) {
     System.out.println("********** Robot program starting **********");
 
     T robot;
     try {
-      robot = robotSupplier.get();
+      robot = constructRobot(robotClass);
     } catch (Throwable throwable) {
       Throwable cause = throwable.getCause();
       if (cause != null) {
@@ -366,10 +392,9 @@ public abstract class RobotBase implements AutoCloseable {
   /**
    * Starting point for the applications.
    *
-   * @param <T> Robot subclass.
-   * @param robotSupplier Function that returns an instance of the robot subclass.
+   * @param robotClass Robot subclass type.
    */
-  public static <T extends RobotBase> void startRobot(Supplier<T> robotSupplier) {
+  public static void startRobot(Class<? extends RobotBase> robotClass) {
     // Check that the MSVC runtime is valid.
     WPIUtilJNI.checkMsvcRuntime();
 
@@ -391,7 +416,7 @@ public abstract class RobotBase implements AutoCloseable {
       Thread thread =
           new Thread(
               () -> {
-                runRobot(robotSupplier);
+                runRobot(robotClass);
                 HAL.exitMain();
               },
               "robot main");
@@ -411,7 +436,7 @@ public abstract class RobotBase implements AutoCloseable {
         Thread.currentThread().interrupt();
       }
     } else {
-      runRobot(robotSupplier);
+      runRobot(robotClass);
     }
 
     // On RIO, this will just terminate rather than shutting down cleanly (it's a no-op in sim).