Fix Multiple Shutdown Callback for Profile with STS Code Path

[waahm7]

*Issue#: awslabs/aws-crt-swift#280
Description of changes:

• Shutdown options were copied over to the sts chain due to a bug. Change the struct copy to explicit fields instead of a shallow copy. Due to the shutdown options copy, we were triggering the shutdown callback multiple times.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 80.36%. Comparing base (e930f1a) to head (18d42c0).

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #251   +/-   ##
=======================================
  Coverage   80.36%   80.36%           
=======================================
  Files          33       33           
  Lines        6044     6045    +1     
=======================================
+ Hits         4857     4858    +1     
  Misses       1187     1187           

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