Delay check as to whether Log.Logger is Reloadable.

[p-m-j]

This allows for slightly more flexible setups, i.e creating a bootstrap logger after the call to HostBuilder.UseSerilog.

[nblumhardt]

Thanks for the PR. We'll need to give this some thought; the moved comment indicates that the design choice was deliberate, not sure what the downsides of the change might be 🤔