🐛Converts appending, and constructors to take in AbstractMotor& instead of MotorGroup&

[noam987]

Summary:

Converts appending, and constructors to take in AbstractMotor& instead of MotorGroup&

Motivation:

Was an oversight originally. It makes sense that motors and custom abstract motors can be appended to MotorGroups. Note it does NOT call the functions of the references being passed in, it just copies over port and reversal information

References (optional):

Test Plan:

• [x] Compiles.

• [x] ` pros::Motor m1(1); pros::Motor m2(2); pros::Motor m3(-3); pros::MotorGroup mg(m1); printf("Expected outputs: 1, 2, -3, 1. Actual outputs: %d, %d, %d, %d\n", m1.get_port(), m2.get_port(), m3.get_port(), mg.get_port());

  pros::MotorGroup mg2({}); mg2.append(m3); mg2 += mg; auto ports = mg2.get_port_all(); printf("Expected outputs: -3, 1, Actual outputs: %d, %d\n", ports[0], ports[1]); } `

[noam987]

Passed hardware testing in beta server