TSL: Add increment and decrement and fix unsual for() expression syntax for transpiler

[Mugen87]

Related issue: #30908

Description

The PR removes the While syntax from TSLEncoder which does not exist. for loops are now always transpiled to TSL with Loop.

[sunag]

Conditionals are important to maintain consistency, in case for() has unusual expressions. I'm checking the possibility of implementing increment() in this PR.

[github-actions]

📦 Bundle size

Full ESM build, minified and gzipped.

	Before	After	Diff
WebGL	336.49 78.38	336.49 78.38	+0 B +0 B
WebGPU	542.05 150.13	542.4 150.23	+354 B +105 B
WebGPU Nodes	541.51 150.03	541.87 150.13	+354 B +106 B

🌳 Bundle size after tree-shaking

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

	Before	After	Diff
WebGL	465.42 112.22	465.42 112.22	+0 B +0 B
WebGPU	614.89 166.17	615.18 166.24	+290 B +65 B
WebGPU Nodes	569.88 155.58	570.17 155.68	+290 B +92 B