Remove the use of expect in `with_aws_sigv4`

**Is your feature request related to a problem or challenge? Please describe what you are trying to do.**
Object store requests using AWS/Azure panic if the HTTP request builder failed.
It would be better and easier to handle if it returned an error instead.

**Describe the solution you'd like**
Replace the `expect` call by an error.

**Describe alternatives you've considered**
I've considered wrapping the s3 client requests with catch_unwind but it's cumbersome.

**Additional context**
aws/credential.rs line 366
azure/credential.rs line 291
client/retry.rs line 450

I can work on the PR.

Start by reading the `expect` call sites at aws/credential.rs:366, azure/credential.rs:291, and client/retry.rs:450, then trace how their HTTP request-building results are handled. Done means those failures are returned as errors from the affected object-store requests rather than causing a panic.

Written by the indexing model from the issue text.