Add ability to get Rotation2d as Measurement<Angle>

[TaylerUva]

Is your feature request related to a problem? Please describe.
My team is trying to convert our code to use Measure as a way to combat usage of incorrect units being used. Rotation2d currently has a constructor that allows creation via Measure<Angle> but no way to get a Measure<Angle> back.

allwpilib/wpimath/src/main/java/edu/wpi/first/math/geometry/Rotation2d.java

Lines 76 to 83 in 25ad6ea

	/**
	* Constructs a Rotation2d with the given angle.
	*
	* @param angle The angle of the rotation.
	*/
	public Rotation2d(Measure<Angle> angle) {
	this(angle.in(Radians));
	}

Describe the solution you'd like
I suggest the following method be implemented within the Rotation2d class

  /**
   * Returns the angle measurement of the Rotation2d.
   *
   * @return The angle measurement of the Rotation2d.
   */
  public Measure<Angle> getMeasure() {
    return Radians.of(getRadians());
  }

Describe alternatives you've considered
A current alternative is to create a new Measure using Units.Rotations.of(Rotation2d.getRadians()) but this is less clean than Rotation2d.getMeasure()

Additional context
None