Resolves error in prior logic

[heckj]

Overlay imports don't accurately describe the graph name they're modifying in the graph, so when ever we have bystanders, we need to use the parsing of the URL name for the relevant module being extended. This PR updates the prior logic and fixes the test that incorrectly asserting that [email protected] were symbols that extended the "A" module, when the extend the "B" module.

Summary

In the prior logic, incorrectly ported from the shadowed logic in DocC, the symbol graphs were trusted to correctly report the module they extend as the "name" of the module. But in the case of one side of overlay
imports, that isn't correct. This updates the logic, and the incorrect test assertion, to reflect that symbols
in the graph named [email protected] extend the module B, not module A , which is in the name property of the graph itself, with B as a bystander.

Dependencies

none

Testing

Included unit test illustrates the issue

Checklist

Make sure you check off the following items. If they cannot be completed, provide a reason.

• Added tests
• Ran the ./bin/test script and it succeeded

[heckj]

@swift-ci please test

[QuietMisdreavus]

Thanks for looking into this!

[QuietMisdreavus]

I went ahead and merged this to try to unblock CI for the toolchain.