improve movement terminology

[supersaiyansubtlety]

rename "movement speed" things -> "acceleration factor"

They're used to calculate the vector added to velocity:

// Entity
public void updateVelocity(float accelerationFactor, Vec3d movementInput) {
    Vec3d lv = movementInputToAcceleration(movementInput, accelerationFactor, this.m_ndosmusf());
    this.setVelocity(this.getVelocity().add(lv));
}

Also, it didn't make sense for higher slipperiness to reduce the result of this method (formerly named getMovementSpeed):

// LivingEntity
private float getAccelerationFactor(float slipperiness) {
    return this.isOnGround() ? this.getBaseAccelerationFactor() * (0.21600002F / (slipperiness * slipperiness * slipperiness)) : this.getAirAccelerationFactor();
}

... but it does make sense for slipperiness to reduce acceleration.

[github-actions]

🚀 Target branch has been updated to 1.21.2-pre5

[github-actions]

🚀 Target branch has been updated to 1.21.2-rc1

[ix0rai]

looks great!

[github-actions]

🚀 Target branch has been updated to 1.21.2

[github-actions]

🚀 Target branch has been updated to 1.21.3