Align Network filter bar features, disable UI experiment

[huntie]

Summary

Follows #154.

Changing my mind: Let’s keep the current Network panel filter bar UI, which fits better with the reduced density of options under React Native. Whenever Chrome ships/abandons NETWORK_PANEL_FILTER_BAR_REDESIGN, we’ll follow. The extra forked code path shouldn’t matter massively — after this diff we support both.

Test plan

✅ Legacy filter bar shown
✅ Intended filters are hidden

• This change maintains backwards compatibility with previous Local Storage data (if modifying settings, experiments, or other persisted client state).

Upstreaming plan

• This commit should be sent as a patch to the upstream devtools-frontend repo. I've reviewed the contribution guide.
• This commit is React Native-specific and cannot be upstreamed.