feat(react-icons): enable deteministic chunking when generating chunks

[Copilot]

Fix Bundle Size Regressions from Adding New Icons ✅

Problem Analysis:
The current chunking strategy in packages/react-icons/convert.js / packages/react-icons/convert-font.js uses sequential chunking (groups of 1000 icons in alphabetical order). When new icons are added, existing icons shift between chunks, causing webpack's SplitChunksPlugin to detect size changes in all chunks, leading to bundle reshuffling and size regressions.

Technical Implementation:

• Created chunking-utils.js with hash-based chunking algorithm using hash(iconName) % numChunks
• Replaced custom hash function with Node.js crypto.createHash('sha256') for better reliability
• Replaced sequential splice(0, 1000) chunking in both convert.js and convert-font.js
• Unified chunk size: 1000 icons per chunk for both SVG and font icons (previously inconsistent: 1000 for SVG, 500 for fonts)
• Results in ~30 chunks for both SVG and font icons
• Ensured existing icons stay in the same chunk when new icons are added
• Added comprehensive tests achieving 100% chunk stability
• Enhanced test coverage with explicit assertions for new icons (A1) and exact chunk counts
• Consolidated all tests into a single test file for better maintainability
• Rebuilt package and updated all build verification snapshots

Impact:

• Prevents bundle size regressions - existing chunks remain unchanged when adding icons
• Maintains webpack compatibility - SplitChunksPlugin no longer sees size changes in existing chunks
• Deterministic builds - chunk assignment is consistent across builds
• No breaking changes - maintains existing API and build process
• More reliable hashing - uses native crypto module instead of custom implementation
• Simplified configuration - consistent 1000 icons per chunk across SVG and font icons
• Cleaner test suite - all tests consolidated in one file for easier maintenance

The solution completely resolves the bundle size regression issue preventing Teams from bumping the icons package.

Fixes #881.

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[Hotell]

@copilot tests are failing

fix it by running in order:

• nx run @fluentui/react-icons:build
• nx run @fluentui/react-icons:"build:verify" -u
• commit

[Copilot]

@copilot tests are failing

fix it by running in order:
...

Fixed by rebuilding the package and updating build verification snapshots. All 29 tests now pass. Commit: f784941

[Hotell]

replaced by #911