Added optional 'Log' property to HttpExceptionMapping for
specifying logging behavior. Introduced static readonly
properties for default mappings of BadRequestException and
NotFoundException using a default message factory.
Updated `GlobalExceptionHandlerOptions` to use a new `_registeredMappings` dictionary for `HttpExceptionMapping` objects, enhancing flexibility in mapping exceptions to HTTP responses. Renamed `RegisterException` to `Add` to reflect its new functionality. Removed the `HttpResponse` record definition and introduced a new `HttpExceptionMapping` record, which includes a static `Create` method for easier instantiation of mappings.
