Add tests for propagation of type constraints in type inference

Description

This PR adds tests that prove that #6379 is fixed. The actual fix happened in #6490.

Closes #6379.

[x] I have linked to any relevant issues.
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[ ] I have updated the documentation where relevant (API docs, the reference, and the Sway book).
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[x] I have added tests that prove my fix is effective or that my feature works.
[ ] I have added (or requested a maintainer to add) the necessary Breaking* or New Feature labels where relevant.
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