[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.

wpilibjExamples/src/main/java/org/wpilib/examples/romireference/Main.java

@@ -1,25 +0,0 @@
-// Copyright (c) FIRST and other WPILib contributors.
-// Open Source Software; you can modify and/or share it under the terms of
-// the WPILib BSD license file in the root directory of this project.
-
-package org.wpilib.examples.romireference;
-
-import org.wpilib.framework.RobotBase;
-
-/**
- * Do NOT add any static variables to this class, or any initialization at all. Unless you know what
- * you are doing, do not modify this file except to change the parameter class to the startRobot
- * call.
- */
-public final class Main {
-  private Main() {}
-
-  /**
-   * Main initialization function. Do not perform any initialization here.
-   *
-   * <p>If you change your main robot class, change the parameter type.
-   */
-  public static void main(String... args) {
-    RobotBase.startRobot(Robot::new);
-  }
-}