Add support for configurable log level for http logging

### Is your feature request related to a problem? Please describe.

I'd like to log the request with the `Error` log level when the response status is 4xx or 5xx, for others log as `Information`.

### Describe the solution you'd like

Currently, the log level is `Information` as I could see, maybe we could add a delegate to decide the logLevel in the `HttpLoggingOptions`, and keep it as `Information` by default

``` c#
public Func LogLevelFactory { get; set; } = context => LogLevel.Information;
```