arrow

GH-39318: [C++][FS][Azure] Add workload identity auth configuration (#39319)



### Rationale for this change
Workload identity is a useful Azure authentication method.

### What changes are included in this PR?
Implement `AzureOptions::ConfigureWorkloadIdentityCredential`

### Are these changes tested?
Added a simple test initialising a fileystem using `ConfigureWorkloadIdentityCredential`. This is not the most comprehensive test but its the same as what we agreed on for https://github.com/apache/arrow/pull/39263. 

### Are there any user-facing changes?
Workload identity authentication is now supported. 

* Closes: #39318

Authored-by: Thomas Newton <thomas.w.newton@gmail.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>