Add ProfiledPIDController with feedforward snippets

[jasondaming]

Adds snippets demonstrating ProfiledPIDController usage with SimpleMotorFeedforward using the two-parameter calculate(currentVelocity, nextVelocity) method.

Changes

• Added Java snippet: wpilibjExamples/src/main/java/edu/wpi/first/wpilibj/snippets/profiledpidfeedforward/Robot.java
• Added C++ snippet: wpilibcExamples/src/main/cpp/snippets/ProfiledPIDFeedforward/cpp/Robot.cpp

Purpose

These snippets will be used in frc-docs (wpilibsuite/frc-docs#3117) to document the recommended feedforward pattern with ProfiledPIDController, replacing deprecated inline code examples.

The snippets demonstrate:

• Using ProfiledPIDController to control motor position
• Tracking previous velocity with a member variable
• Using feedforward.calculate(lastSpeed, controller.getSetpoint().velocity) pattern
• Complete, compilable robot code

Related

• frc-docs PR: Replace deprecated feedforward.calculate(velocity, acceleration) frc-docs#3117
• frc-docs issue: ElevatorFeedforward.calculate(double velocity, double acceleration) is depecated for removal frc-docs#2963

[sciencewhiz]

There's a list of valid tags here:

allwpilib/shared/examplecheck.gradle

Lines 45 to 85 in 2fb5271

	def tagList = [
	/* --- Categories --- */
	// On-RIO image processing
	"Vision",
	// Command-based
	"Command-based",
	// Romi
	"Romi",
	// XRP
	"XRP",
	// Extremely simple programs showcasing a single hardware API
	"Hardware",
	// Full robot, with multiple mechanisms
	"Complete Robot",
	// A single mechanism in the Robot class
	"Basic Robot",
	/* --- Mechanisms --- */
	"Intake", "Flywheel", "Elevator", "Arm", "Differential Drive", "Mecanum Drive",
	"Swerve Drive",
	/* --- Telemetry --- */
	"SmartDashboard", "Shuffleboard", "Sendable", "DataLog",
	/* --- Controls --- */
	"Exponential Profile", "PID", "State-Space", "LTVUnicycleController", "Path Following",
	"Trajectory", "SysId", "Simulation", "Trapezoid Profile", "Profiled PID", "Odometry",
	"LQR", "Pose Estimator",
	/* --- Hardware --- */
	"Analog", "Ultrasonic", "Gyro", "Pneumatics", "I2C", "Duty Cycle", "PDP", "DMA", "Relay",
	"AddressableLEDs", "HAL", "Encoder", "Smart Motor Controller", "Digital Input",
	"Digital Output", "Accelerometer",
	/* --- HID --- */
	"XboxController", "PS4Controller", "PS5Controller", "Joystick",
	/* --- Misc --- */
	/* (try to keep this section minimal) */
	"EventLoop", "AprilTags", "Mechanism2d", "Preferences",
	]

[Gold856]

How long is this expected to last? Last I checked, we're trying to axe ProfiledPIDController in favor of just using TrapezoidProfile and PIDController.