Add FXMacroData OHLCV provider

[roberttidball]

Summary

Adds a native FXMacroDataOHLCVDataProvider for daily FX reference-rate series from the FXMacroData REST API.

The provider:

• supports market="FXMACRODATA" with daily 1d data sources
• accepts symbols such as EURUSD and EUR/USD
• maps FXMacroData close-only daily reference values into the framework OHLCV schema by setting Open/High/Low/Close to the same value and Volume to 0
• supports API keys via MarketCredential(market="FXMACRODATA", api_key="..."), FXMACRODATA_API_KEY, or FXMD_API_KEY
• is registered with the default data-provider lists and documented with the existing market-data-source docs

Validation

• python -m pytest tests\infrastructure\data_providers\test_fxmacrodata_ohlcv_data_provider.py -q
• python -m compileall -q investing_algorithm_framework\infrastructure\data_providers\fxmacrodata.py
• git diff --check

[MDUYN]

Hey @roberttidball, it seems that your PR is still in draft mode.