feat(common): allow default currency code to be configurable (#32584)

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 #32584

tools/public_api_guard/core/core.d.ts

@@ -257,6 +257,8 @@ export declare const DebugNode: {
     new (...args: any[]): DebugNode;
 };
 
+export declare const DEFAULT_CURRENCY_CODE: InjectionToken<string>;
+
 /** @deprecated */
 export declare class DefaultIterableDiffer<V> implements IterableDiffer<V>, IterableChanges<V> {
     readonly collection: V[] | Iterable<V> | null;