We don't need nested hashes there. A single hash is enough, and we also
don't need to key it by pointers. Keying it by internalName instead
makes the ordering deterministic. We also don't need to duplicate-track
the variable names when outputting the declarations anymore.
Verify that qmlcachegen's output is actually stable by compiling the
entire test data for tst_qmlcppcodegen twice, packaging the generated
code into the resource file system, and comparing it in a separate test.
Pick-to: 6.5 6.6
Fixes: QTBUG-115159
Change-Id: I659661e58a52ed9ff308c83d6c821cf016f2e94e
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>
Ulf Hermann