Speed up generated JS demos check

[EugeniyKiyashko]

No description provided.

[Copilot]

Pull request overview

Speeds up the "Check generated JS demos" CI step by (1) running the TS→JS conversion only when there are changed React demos, (2) batching prettier/eslint formatting across all generated outputs in chunks of 50 instead of per-demo, and (3) parallelizing demo conversions with a configurable concurrency. Also adds error propagation so failed conversions cause the job to exit non‑zero, adds module declaration files needed for two VectorMap React demos to compile, and reduces the visual-tests matrix from 5 to 2 shards.

Changes:

• Refactor converter.ts/cli.ts: extract prettifyOutputs, run conversions in concurrent batches (CONVERT_TO_JS_CONCURRENCY, default 8), surface failures via exit code, and stream tsc stdout/stderr on failure.
• Simplify workflow: pre-compute changed React demo list once, gate all dependent steps on has-react-demos, and feed the list to pnpm run convert-to-js via xargs.
• Add type declarations for devextreme-dist/js/vectormap-data/{world,usa}.js and adjust a style typing in Diagram/AdvancedDataBinding/React/App.tsx to support TS→JS conversion.

Reviewed changes

Copilot reviewed 4 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
apps/demos/utils/ts-to-js-converter/converter.ts	Adds shell-quoting/posix helpers, chunked prettifyOutputs, returns boolean from converter, prints tsc output on failure, sets preserveSymlinks.
apps/demos/utils/ts-to-js-converter/cli.ts	Adds concurrency-controlled batching, collects out dirs, runs prettifyOutputs once at the end, exits non‑zero on failures.
.github/workflows/visual-tests-demos.yml	Pre-detects changed React demos, gates steps on the result, calls converter once via xargs; visualtests matrix changed from 5 to 2 shards.
apps/demos/Demos/Diagram/AdvancedDataBinding/React/App.tsx	Replaces React.CSSProperties typing with a plain object shape for itemStyleExpr.
apps/demos/Demos/VectorMap/MultipleLayers/React/devextreme-vectormap-data.d.ts	New ambient module declaration for world.js vector map data.
apps/demos/Demos/VectorMap/ImageMarkers/React/devextreme-vectormap-data.d.ts	New ambient module declaration for usa.js vector map data.