Implement exception handling when using search providers

[exileDev]

nopCommerce version: develop

Currently SearchProductsAsync method of ProductService doesn't handle any exceptions thrown by search providers (see https://github.com/nopSolutions/nopCommerce/blob/develop/src/Libraries/Nop.Services/Catalog/ProductService.cs#L910).

Let's add a setting indicating whether to return default search results when a search provider throws an exception