[Feature Request] Allow tags to be auto-populated as hints in dropdown when searching using tag-keys in search bar in haystack UI

[doctorXWrites]

• If a user wants to search for say given page-name in the universal search bar, currently auto-populate is not supported so there are no hints, and one needs to know the exact value to be able to search.
• These should be configurable as to for what tag-keys this feature is being switched on since one would simply not want to put pressure of all the tags on the system.

[shreyaa-sharma]

@doctorXWrites : Can you get the PR reviewed and close the issue.