feat: Expose bucket_namespace output (References #390)

[sharansutrapu]

Description

While bucket_namespace was recently added to the module's variables and main resource block, it was unfortunately left out of outputs.tf. This PR exposes s3_bucket_bucket_namespace so downstream consumers can reference the namespace natively.

Note regarding Issue #390: I originally looked at implementing the auto-suffixing logic for bucket_prefix requested in #390. However, because Terraform natively appends its random hex generation to the absolute end of the bucket_prefix string (and AWS requires -an at the absolute end), automatically handling this would require overriding the native provider behavior and generating custom random_string resources within the module. I deferred implementing that to avoid introducing brittle string manipulation, but wanted to get this missing output up for review!

Motivation and Context

Completes the integration of the bucket_namespace variable. References #390.

Breaking Changes

None.

How Has This Been Tested?

• Verified via terraform validate that the output mapping evaluates perfectly.
• Executed a full terraform plan, apply, and destroy cycle against a live AWS environment. Confirmed that the AWS API successfully provisions account-regional buckets via the module and that the output correctly exports the state.