Timer: Move into core.

[Mugen87]

Related issue: #30497

Description

As suggested in #30497 (comment), this PR moves THREE.Timer into the core as the successor for THREE.Clock.

Ideally, THREE.Clock with its conceptual flaws is deprecated in the future.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	338.36 78.95	338.37 78.95	+6 B +3 B
WebGPU	557.72 154.42	557.72 154.42	+6 B +2 B
WebGPU Nodes	556.64 154.2	556.64 154.2	+6 B +3 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	469.6 113.66	469.6 113.66	+0 B +0 B
WebGPU	633.39 171.45	633.39 171.45	+0 B +0 B
WebGPU Nodes	588.52 160.8	588.52 160.8	+0 B +0 B

[mrdoob]

Sounds good to me!