The "updates" key is an alternative "guid" key for fragment profiles.
But SettingsLoader::_appendProfile stores and deduplicates profiles according
to their "guid" only. We need to modify the function to optionally store
profiles by their "updates" key as well, otherwise multiple fragment
profiles without "guid" might collide as they produce the same default GUID.
## PR Checklist
* [x] Closes#11597
* [x] I work here
* [ ] Tests added/passed
* [ ] Schema updated.
* [ ] I've discussed this with core contributors already. If not checked, I'm ready to accept this work might be rejected in favor of a different grand plan. Issue number where discussion took place: #xxx
## Validation Steps Performed
* Unit tests pass ✔️
* Issue #11597 doesn't reproduce anymore ✔️
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