CurveCalibrator hardcodes MarketDataFxRateProvider for FX rate resolution

[traggatt]

Configuration of the FX rate resolution strategy was previously exposed via the now pkg-private overload of calibrate() by passing a RatesProvider explicitly. It would be useful to allow the caller to pass an FxRateProvider explicitly.

Other places hardcoding MarketDataFxRateProvider.of() should also be modified to allow more flexibility.

[traggatt]

Also spotted here:

Strata/modules/data/src/main/java/com/opengamma/strata/data/scenario/DefaultScenarioFxRateProvider.java

Line 46 in d030094

return MarketDataFxRateProvider.of(marketData.scenario(scenarioIndex), source);

[cjkent]

This is related to #1417. The solution is to consistently use MarketData to hold FX rates and avoid FxMatrix.