Preserve trailing zeros in Money and RoundedMoney (#438)

[joao-loureiro-ig]

Fixes #438.

Problem

See #438 for details.

Change

• ConvertBigDecimal — make Number → BigDecimal conversion faithful (remove stripScalingZeroes). This alone makes Money and RoundedMoney preserve scale on construction, getNumber() read-back, the amount-factory path, and arithmetic results, with no changes needed to Money/RoundedMoney.
• FastMoney's behaviour is intentionally unchanged. Its fixed-scale long representation is lossy (1.42 and 1.420 both map to 142000), so it cannot carry trailing zeros. The stripping it used to get implicitly is moved into MoneyUtils.stripScalingZeroes(...) and applied explicitly where needed, keeping its behaviour identical.

Behavioural notes

• toString() now shows preserved zeros for Money/RoundedMoney (e.g. "USD 1.420", "CHF 1234.0").
• Arithmetic results keep BigDecimal's natural scale (e.g. a remainder may read as 0.5000000000000000; 1000 × 28.456 → 28456.000).
• NumberValue.getAmountFractionNumerator() returns a long, so for a factory-built Money at very high scale it can now throw on overflow where stripping previously reduced the scale (the spec permits exact-style accessors to throw on non-representable values).

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