Nodes: Optimize getCacheKey().

[Mugen87]

Related issue: -

Description

Nodes.getCacheKey() is executed at least once per render call so it make sense to optimize this code path as good as possible. This PR does two things:

• It introduces a module scope array _cacheKeyValues for managing the values that are used to compute the cache key. Previously, an array was created every time a new cache key was required.
• It only creates the object that holds the cache key data when necessary. Most of the time, existing objects can be updated.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	339.49 79.09	339.49 79.09	+0 B +0 B
WebGPU	489.83 135.88	489.83 135.89	+6 B +11 B
WebGPU Nodes	489.29 135.77	489.3 135.78	+6 B +10 B

🌳 Bundle size after tree-shaking

Minimal build including a renderer, camera, empty scene, and dependencies.

	Before	After	Diff
WebGL	465.35 112.14	465.35 112.14	+0 B +0 B
WebGPU	559.31 151.37	559.31 151.38	+6 B +6 B
WebGPU Nodes	515.38 141.15	515.39 141.16	+6 B +15 B