[object_store] Runtime Agnostic Retry Machinery

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

Whilst the HttpClient abstraction allows spawning work to a separate tokio runtime, see apache/arrow-rs#7253, the retry machinery itself also makes use of tokio - see [here](https://github.com/apache/arrow-rs/blob/main/object_store/src/client/retry.rs#L361).

This forces the calling context to be a tokio content.

**Describe the solution you'd like**

I think we should make it possible to use object_store in a non-tokio runtime.

**Describe alternatives you've considered**

We could simply disable backoff and rety if not called from a tokio runtime.

**Additional context**

Read object_store/src/client/retry.rs around line 361 and the HttpClient abstraction referenced in the issue. Trace how retry and backoff are invoked and identify the Tokio runtime assumptions; done means object_store can be used from a non-Tokio runtime while retaining retry behavior.

Written by the indexing model from the issue text.