Support Swift CXX Interop

[waahm7]

Issue #, if available:
awslabs/aws-crt-swift#166

Description of changes:

• Don't include inl files as part of extern C. We use AWS_EXTERN_C_BEGIN and AWS_EXTERN_C_END within the inl files.
• Ideally, we should add CI in common as well, but I don't know how. I will add CI in crt-swift.

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 83.84%. Comparing base (f58e807) to head (220324f).

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1160   +/-   ##
=======================================
  Coverage   83.84%   83.84%           
=======================================
  Files          57       57           
  Lines        5992     5992           
=======================================
  Hits         5024     5024           
  Misses        968      968           

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