Allow specifying PUT options when using BufWriter

[netthier]

Is your feature request related to a problem or challenge? Please describe what you are trying to do.

I want to specify attributes for objects uploaded via the BufWriter interface.

Describe the solution you'd like

I'd like to be able to pass options similar to those accepted by put_opts and put_multipart_opts to a new BufWriter instance.

Describe alternatives you've considered

An alternative would be to use put_opts and put_multipart_opts directly, but I'd prefer not to re-implement the BufWriter interface. Alternatively the options could be set on the object after the fact, though I'm unsure how that can be done with this crate.

[tustvold]

label_issue.py automatically added labels {'object-store'} from #5693