feat[security]: Don't use environment configurations unless explicitly enabled

Currently some services, such as Azure-Storage, have no option to disable the use of workload identities.
This is a security risk as any binary that includes reqsign can access, without further configurations, files, the host machine has access to. For server applications this is problematic.
Instead, we should opt to a secure default, that is, users must specify credentials explicitly. Environment Credentials must be opt-in for security reasons alone, just like they are in all Cloud SDKs.

I think we should start by adding options to disable environment configuration first (Just like S3 which already has it), and switch to secure defaults in the next major release.

Start by comparing the existing S3 option for disabling environment configuration with the Azure-Storage and workload-identity paths described in the issue. Identify which services need an explicit opt-in and define completion as equivalent disable options being available, while keeping the secure-default change for the next major release.

Written by the indexing model from the issue text.