[IMPROVE] obb.equity.screener: Make Input Of Country & Exchange Uniform Across Providers

[deeleeramone]

In the economy module, the country parameter can be entered as names or two-letter ISO codes. The same treatment should be applied to the obb.equity.screener endpoint. Additionally, the "exchange" parameter should reference ISO MICs - i.e, XNAS instead of NASDAQ, XNYS instead of NYSE, etc.