Default currency code in CurrencyPipe is currently hardcoded to USD
and is not configurable. This commit allows the default currency code
to be configurable by adding a DEFAULT_CURRENCY_CODE injection token.
Example:
```
providers: [{ provide: DEFAULT_CURRENCY_CODE, useValue: "GBP" }]
...
{{ 123.45 | currency }} // outputs £123.45 as opposed to always $123.45 before
```
Closes: #25461
PR Close#34771
965f5575c7