object_store: Export ClientConfigKey and add HttpBuilder::with_config

[thehabbos007]

Which issue does this PR close?

Closes #4515

Rationale for this change

The changes here are to enable more consistent use of the different providers in the object_store crate. It would be useful for polars to have access to this to make implementing http more consistent with the rest. See https://github.com/pola-rs/polars/blob/96b0e07e75a882eaed7be05e619307bc144aa5b4/polars/polars-core/src/cloud.rs

What changes are included in this PR?

• Exporting ClientConfigKey
• Add HttpBuilder::with_config

Are there any user-facing changes?

There are user facing changes, but not breaking. The addition has been documented.

[tustvold]

This makes sense to me, my only thought is whether we would potentially in the future want to add options unique to the HttpStore and not found on ClientOptions. This would entail a HttpConfigKey or something, I don't feel strongly either way

[thehabbos007]

Yeah, that was an alternative considered in the issue linked. I think that would be ideal, but for I don't expect there to be special casing for HTTP. Could be in the future, though :)