perf: improve too many user api call

[keita-determined]

Description

DET-7962

Test Plan

• Check if user api call is reduced (user api call less than 5 times before polling starts in network tab)
  • user api used to be called more than 5 times before polling starts
• Check if user data is fetched appropriately instead of no user data

Commentary (optional)

Checklist

• User-facing API changes need the "User-facing API Change" label.
• Release notes should be added as a separate file under docs/release-notes/.
  See Release Note for details.
• Licenses should be included for new code which was copied and/or modified from any external code.
• If modifying /webui/react/src/shared/ verify make -C webui/react test-shared passes.

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[keita-determined]

test-cli is failed. I believe that it should fail cuz the code change is not related to what ci tests

[keita-determined]

When lots of user avatars is rendered at once fetchUsers is called many times, so fetchUsers is moved in App.tsx and call once.
This implementation should be fine because lots of components is polling fetchUsers every few seconds

[gt2345]

LGTM