Switch Framework/SINQ to generated DllConfig.h

[peterfpeterson]

As part of the effort to reduce compile time, change SINQ to use a generated DllConfig.h and remove MantidKernel/System.h from unit tests.

Refs #38457.

To test:

This is a simple refactor so the automated tests should continue to pass.

This does not require release notes because it is a refactor.

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