[SymbolGraphGen] only include the given symbol for qualified imports (#59852)

* only include the given symbol for qualified imports

rdar://96309088

* re-exporting one type should not allow unrelated types to sneak in

* ensure that children of re-exported types are also re-exported

test/SymbolGraph/Module/Inputs/QualifiedImportWithExtensions/A.swift

@@ -0,0 +1,5 @@
+public struct StructOne {
+    public init() {}
+}
+
+public struct StructTwo {}