raycast result includes closest hit fraction

[minggo]

#17672

[minggo]

Have to change other physics engines implementation.

[github-actions]

Interface Check Report

! WARNING this pull request has changed these public interfaces:

@@ -48803,21 +48803,36 @@
              * @zh
              * 在世界坐标系下击中面的法线。
              */
             get hitNormal(): math.Vec3;
+            /**
+             * @en
+             * Represents the fraction (range: 0.0 to 1.0) along the ray's path where the closest collision occurs.
+             * A value of 0.0 indicates an immediate collision at the ray's starting point,
+             * while a value of 1.0 means no collision along the entire ray length.
+             * Intermediate values indicate the fraction of the ray distance at which the closest hit is detected.
+             * Warning: only take effect with Bullet.
+             * @zh
+             * 表示射线路径上最近碰撞发生的位置，以百分比形式（范围：0.0 到 1.0）。
+             * 0.0 表示射线在起点处立即发生碰撞，1.0 表示射线在整个路径上未发生碰撞。
+             * 中间值表示碰撞点在射线总长度上的比例位置。
+             * 注意：只在 Bullet 引擎起效.
+             */
+            get closestHitFraction(): number;
             protected _hitPoint: math.Vec3;
             protected _hitNormal: math.Vec3;
             protected _distance: number;
             protected _collider: Collider | null;
+            protected _closestHitFraction: number;
             /**
              * @en
              * internal methods.
              * @zh
              * 设置射线，此方法由引擎内部使用，请勿在外部脚本调用。
              *
              * @deprecated since v3.5.0, this is an engine private interface that will be removed in the future.
              */
-            _assign(hitPoint: math.IVec3Like, distance: number, collider: Collider, hitNormal: math.IVec3Like): void;
+            _assign(hitPoint: math.IVec3Like, distance: number, collider: Collider, hitNormal: math.IVec3Like, closestHitFraction?: number): void;
             /**
              * @en
              * clone.
              * @zh