Fix substituteQualifiedName

[kazcw]

Fix substituteQualifiedName (currently used to simplify names in dropdown widgets).

substituteQualifiedName had two bugs:

• It was incorrectly using the return value of Ast.replaceValue, using the value removed from the module as if it were the new tree.
• It was matching names that are textual prefixes of other names.

Pull Request Description

Important Notes

Checklist

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• The documentation has been updated, if necessary.
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