fix(ui5-illustrated-message): add v5 loader in tnt illustrations

[dobrinyonkov]

Fixes #8145

Problem

When importing a single TNT illustration directly (e.g., import "@ui5/webcomponents-fiori/dist/illustrations/tnt/NoApplications.js"), the IllustratedMessage displayed V4 instead of V5 when using Horizon themes.

Solution

Modified the illustration generation script to register V5/V5-HC loaders for V4 TNT illustrations that have corresponding V5 versions. The loaders use dynamic imports, so V5 SVGs load lazily only when a Horizon theme is active.

Key Points

• Only affects TNT illustrations (fiori set has no V5)
• Checks V5 availability at build time (some TNT illustrations like UnableToLoad have no V5)
• Maintains tree-shaking - only the specific illustration's V5 loader is registered
• No regression for AllIllustrations.js

Design Decisions

Why V4 is imported directly, but V5 is lazy-loaded?

The current approach loads V4 SVGs directly and registers V5 as a lazy loader:

// V4 imported directly (always loaded)
import dialogSvg from "./tnt-Dialog-NoApplications.js";

// V5 loader registered (lazy, loaded only if Horizon theme)
registerIllustrationLoader("tnt/V5/NoApplications", async () => {
  return (await import("../../illustrations-v5/tnt/NoApplications.js")).default;
});

Why not import V5 directly too?

• Theme is determined at runtime, not build time
• Imports execute before any theme detection code runs
• Users can switch themes dynamically at runtime
• Importing both upfront would load unnecessary assets

Why not make both V4 and V5 lazy?
This would require moving V4 assets to a dedicated illustrations-v4/ folder and restructuring the illustration files to only register loaders. However:

• would not be compatible for users who import SVGs directly (import { dialogSvg } from "...tnt/NoApplications.js")

[plamenivanov91]

Is it possible to write cypress test and test for the SVG in the DOM in order to support this complex logic ?