Summary
Make code and build changes to enable running S3 extension on Windows.

Motivation
Some effort was done as part of WT-8720 to get the extension compiling and working on Windows. There is a PR linked to that ticket and some comments detailing where the efforts were. Continue the work and get the extension working on windows. Also add the testing to a windows test variant on evergreen, if it makes sense to do so. Python tests for tiered storage (including local_store) are skipped on Windows for now, because of the way extensions are loaded as external libraries. Possibly they can be supported if the extension is built-in on Windows?

This work should only be done if the benefits of testing on Windows and making the build system and code platform-independent outweighs the effort involved.

Note:
Do consider the costs involved in interacting with S3. Aim for a balance between the costs and benefits.

• Is this issue urgent?
  No

Acceptance Criteria (Definition of Done)
The extension builds (and tests) on Windows. Evergreen has some form of testing for S3 on windows.