Expand ArmorStand API

Adds the following:
- Add proper methods for getting and setting items in both hands. Deprecates old methods
- Enable/Disable slot interactions
- Allow using degrees for ArmorStand rotations (via new Rotations class)

Co-authored-by: SoSeDiK <mrsosedik@gmail.com>

paper-api/src/main/java/io/papermc/paper/math/Rotations.java

@@ -0,0 +1,101 @@
+package io.papermc.paper.math;
+
+import org.jspecify.annotations.NullMarked;
+
+/**
+ * Rotations is an immutable object that stores rotations
+ * in degrees on each axis (X, Y, Z).
+ */
+@NullMarked
+public interface Rotations {
+
+    /**
+     * Rotations instance with every axis set to 0
+     */
+    Rotations ZERO = ofDegrees(0, 0, 0);
+
+    /**
+     * Creates a new Rotations instance holding the provided rotations
+     *
+     * @param x the angle for the X axis in degrees
+     * @param y the angle for the Y axis in degrees
+     * @param z the angle for the Z axis in degrees
+     * @return Rotations instance holding the provided rotations
+     */
+    static Rotations ofDegrees(final double x, final double y, final double z) {
+        return new RotationsImpl(x, y, z);
+    }
+
+    /**
+     * Returns the angle on the X axis in degrees
+     *
+     * @return the angle in degrees
+     */
+    double x();
+
+    /**
+     * Returns the angle on the Y axis in degrees
+     *
+     * @return the angle in degrees
+     */
+    double y();
+
+    /**
+     * Returns the angle on the Z axis in degrees
+     *
+     * @return the angle in degrees
+     */
+    double z();
+
+    /**
+     * Returns a new Rotations instance which is the result
+     * of changing the X axis to the passed angle
+     *
+     * @param x the angle in degrees
+     * @return the resultant Rotations
+     */
+    Rotations withX(double x);
+
+    /**
+     * Returns a new Rotations instance which is the result
+     * of changing the Y axis to the passed angle
+     *
+     * @param y the angle in degrees
+     * @return the resultant Rotations
+     */
+    Rotations withY(double y);
+
+    /**
+     * Returns a new Rotations instance which is the result
+     * of changing the Z axis to the passed angle
+     *
+     * @param z the angle in degrees
+     * @return the resultant Rotations
+     */
+    Rotations withZ(double z);
+
+    /**
+     * Returns a new Rotations instance which is the result of adding
+     * the x, y, z components to this Rotations
+     *
+     * @param x the angle to add to the X axis in degrees
+     * @param y the angle to add to the Y axis in degrees
+     * @param z the angle to add to the Z axis in degrees
+     * @return the resultant Rotations
+     */
+    Rotations add(double x, double y, double z);
+
+    /**
+     * Returns a new Rotations instance which is the result of subtracting
+     * the x, y, z components from this Rotations
+     *
+     * @param x the angle to subtract from the X axis in degrees
+     * @param y the angle to subtract from the Y axis in degrees
+     * @param z the angle to subtract from the Z axis in degrees
+     * @return the resultant Rotations
+     */
+    default Rotations subtract(final double x, final double y, final double z) {
+        return this.add(-x, -y, -z);
+    }
+
+}

paper-api/src/main/java/io/papermc/paper/math/RotationsImpl.java

@@ -0,0 +1,28 @@
+package io.papermc.paper.math;
+
+import org.jspecify.annotations.NullMarked;
+
+@NullMarked
+record RotationsImpl(double x, double y, double z) implements Rotations {
+
+    @Override
+    public RotationsImpl withX(final double x) {
+        return new RotationsImpl(x, this.y, this.z);
+    }
+
+    @Override
+    public RotationsImpl withY(final double y) {
+        return new RotationsImpl(this.x, y, this.z);
+    }
+
+    @Override
+    public RotationsImpl withZ(final double z) {
+        return new RotationsImpl(this.x, this.y, z);
+    }
+
+    @Override
+    public RotationsImpl add(final double x, final double y, final double z) {
+        return new RotationsImpl(this.x + x, this.y + y, this.z + z);
+    }
+
+}