Fix Bundle Size Regressions from Adding New Icons ✅

Problem Analysis:
The current chunking strategy in packages/react-icons/convert.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.

Solution Implemented:

• Analyze current chunking mechanism in convert.js
• Identify root cause: sequential chunking causes icon movement between chunks
• Implement hash-based stable chunking strategy
• Create deterministic chunk assignment based on icon name hash
• Maintain backward compatibility with existing build process
• Add tests to verify chunk stability
• Apply stable chunking to font chunks as well
• Update build verification tests to match new chunk structure
• Add comprehensive bundle size regression prevention tests
• Simplify hash function using native Node.js crypto module
• Standardize chunk size to 1000 icons for both SVG and font icons
• Enhance test assertions with exact values

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
• Simplified test suite by consolidating redundant tests and using clear toEqual assertions

Verification Results:

• ✅ All build verification tests pass (29/29)
• ✅ Chunk stability tests show 100% stability when adding new icons
• ✅ Bundle size regression prevention tests demonstrate complete fix
• ✅ Original icons remain in assigned chunks when new icons are added
• ✅ Even distribution of new icons across existing chunks
• ✅ Consistent chunking configuration across all icon types
• ✅ Clear test assertions using toEqual for better readability

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 - consolidated tests with explicit assertions for better maintainability

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

Fixes #881.

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