* Fix parsing foreign currency strings
Currently parsing a currency string would fail if the currency code does not match `FormatStyle`'s locale region. For example,
```swift
let style = Decimal.FormatStyle.Currency(code: "GBP", locale: .init(identifier: "en_US")).presentation(.isoCode)
```
This formats 3.14 into "GBP\u{0xa0}3.14", but parsing such string fails.
Fix this by always set the ICU formatter's currency code.
Resolves rdar://138179737
* Update the test to throw properly instead of force unwrap
* Remove another force try
* Remove the stored `numberFormatType` and `locale` inside `IntegerParseStrategy` and `FloatingPointParseStrategy`
These properties are redundant as the information is already available through the public variable `formatStyle`.
* Address feedback
* Fix a typo
