Modularize `readVnNumber` function instead of using classes #43

Performance Regression: -85.15%

⚡ 20 improvements
❌ 1 regression
✅ 43 untouched

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

	Benchmark	`BASE`	`HEAD`	Change
⚡	`format order count (1,234)`	31.7 µs	28.6 µs	+10.65%
⚡	`formatVnNumber with different input types`	429.2 µs	45.4 µs	×9.5
⚡	`bigint input (large transaction)`	174 µs	43.3 µs	×4
⚡	`mixed input types in data processing (30 values)`	659.2 µs	272.4 µs	×2.4
⚡	`number input (typical price)`	169.5 µs	39.5 µs	×4.3
⚡	`string input (from API/form)`	172 µs	49.3 µs	×3.5
⚡	`display financial dashboard (20 metrics)`	468 µs	204 µs	×2.3
⚡	`display invoice line items (10 items)`	519.1 µs	183.7 µs	×2.8
⚡	`display payment receipt (typical transaction)`	193 µs	50.9 µs	×3.8
⚡	`display product catalog (20 products)`	739.1 µs	298.6 µs	×2.5
⚡	`display shopping cart (5 items with quantities)`	299.9 µs	120 µs	×2.5
⚡	`read 50 e-commerce prices (10k-50M VND)`	1,409.9 µs	369 µs	×3.8
⚡	`read 50 financial amounts (1M-10B VND)`	1,182 µs	465.4 µs	×2.5
⚡	`read 50 invoice totals (100k-100M VND)`	903.6 µs	362.6 µs	×2.5
❌	`read 50 product quantities (1-100)`	566.3 µs	3,814.3 µs	-85.15%
⚡	`annual revenue (2,500,000,000 VND)`	183 µs	53.8 µs	×3.4
⚡	`invoice total (5,450,000 VND)`	171.5 µs	57.8 µs	×3
⚡	`large contract value (15,000,000,000 VND)`	167.3 µs	49.4 µs	×3.4
⚡	`product quantity (5 items)`	86 µs	66.7 µs	+28.89%
⚡	`transaction amount (19,990,000 VND)`	177.9 µs	53 µs	×3.4
...	...	...	...	...

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