## Context
Noticed that while default opted into unified logs, if you refresh while
on the page, you'll get redirected back to the old logs URL
(logs/explorer)
Happening due to a inconsistent tracking of loading states for feature
flags and feature previews. Just need to track whether the feature
previews have been initialized
<!-- This is an auto-generated comment: release notes by coderabbit.ai
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## Summary by CodeRabbit
* **Bug Fixes**
* Improved the loading behavior for unified logs preview so it only
finishes loading after preview settings are fully initialized.
* Added a more reliable initialization state to better reflect when
feature-based defaults are ready.
<!-- end of auto-generated comment: release notes by coderabbit.ai -->
Joshen Lim
0038f303f2