Summary
Use Catch2 for unit testing S3 extension's S3Connection class.

Motivation
WT-8733 brought in the support for using Catch2 as the preferred unit test framework for WiredTiger. S3 extension can benefit from switching to Catch2. The unit test for S3's connection to AWS are already written in a way that they will easily export to a test framework. This was intentionally done, as we waited for a preferred framework to be supported in WiredTiger's build environment.

• Does this affect any team outside of WT?
  No

• Is this issue urgent?
  No

Acceptance Criteria (Definition of Done)
Existing unit tests for S3 extension run and pass using the Catch2 framework.