Add Vec3 methods to normalize and extract length

[shrinktofit]

Re: #

Changelog

Add following methods to normalize a vec3 and return its length.

• Generic static form: Vec3.normalizeAndExtractLength(out, epsilon = 1e-8)
• Instance form: Vec3.prototype.normalizeSelfAndExtractLength(epsilon = 1e-8)

Usage:

/**
 * Move `source` towards `target`.
 */
function moveTowards(source: Vec3, target: Vec3, maxMovement: number) {
  const dir = Vec3.sustract(new Vec3(), target, source);
  const distance = dir.normalizeSelfAndExtractLength();
  Vec3.scaleAndAdd(source, source, dir, Math.min(distance, maxMovement));
}

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Continuous Integration

This pull request:

• needs automatic test cases check.

  Manual trigger with @cocos-robot run test cases afterward.

• does not change any runtime related code or build configuration

  If any reviewer thinks the CI checks are needed, please uncheck this option, then close and reopen the issue.

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Compatibility Check

This pull request:

• changes public API, and have ensured backward compatibility with deprecated features.
• affects platform compatibility, e.g. system version, browser version, platform sdk version, platform toolchain, language version, hardware compatibility etc.
• affects file structure of the build package or build configuration which requires user project upgrade.
• introduces breaking changes, please list all changes, affected features and the scope of violation.

[github-actions]

Code Size Check Report

Wechat (WASM)	Before	After	Diff
2D Empty (legacy pipeline)	1009805 bytes	1010039 bytes	⚠️ +234 bytes
2D All (legacy pipeline)	2675364 bytes	2675598 bytes	⚠️ +234 bytes
2D All (new pipeline)	2767100 bytes	2767334 bytes	⚠️ +234 bytes
(2D + 3D) All	10024070 bytes	10024304 bytes	⚠️ +234 bytes

Web (WASM + ASMJS)	Before	After	Diff
(2D + 3D) All	16843132 bytes	16843366 bytes	⚠️ +234 bytes

Interface Check Report

! WARNING this pull request has changed these public interfaces:

@@ -14732,8 +14732,16 @@
              * @zh 归一化向量，输入零向量将会返回零向量。
              */
             static normalize<Out extends IVec3Like>(out: Out, a: IVec3Like): Out;
             /**
+             * @en Normalizes the vector and returns the length of the vector before normalization.
+             * @zh 归一化向量并返回归一化前的长度。
+             * @param out 向量。
+             * @param epsilon 用于判定向量长度是否为 0 的阈值。
+             * @returns 归一化前的长度。
+             */
+            static normalizeAndExtractLength<Out extends IVec3Like>(out: Out, epsilon?: number): number;
+            /**
              * @en Calculates the dot product of the vector
              * @zh 向量点积（数量积）
              */
             static dot<Out extends IVec3Like>(a: Out, b: IVec3Like): number;
@@ -15123,10 +15131,17 @@
             /**
              * @en Normalize the current vector.
              * @zh 将当前向量归一化
              */
-            normalize(): Vec3;
+            normalize(epsilon?: number): Vec3;
             /**
+             * @en Normalize the current vector and return its length.
+             * @zh 将当前向量归一化并返回其长度。
+             * @param epsilon 用于判断向量是否为零的阈值。
+             * @returns 向量归一化前的长度（模）。
+             */
+            normalizeSelfAndExtractLength(epsilon?: number): number;
+            /**
              * @en Transforms the vec3 with a mat4. 4th vector component is implicitly '1'
              * @zh 将当前向量视为 w 分量为 1 的四维向量，应用四维矩阵变换到当前矩阵
              * @param matrix matrix to transform with
              */