Instant navs devtools revamp (#94027)
This updates the Instant Navs DevTools panel to better model capture
state across pending, SPA, and MPA navigations.
- Revamps the Navigation Inspector UI states, controls, focus behavior,
and panel transitions
- Resets capture state when closing the panel from active capture states
- Keeps MPA reloads and root-layout-crossing navigations from briefly
showing stale or optimistic SPA state
- Consolidates the panel state flow so cookie state, re-arming, and
rendered UI status are easier to follow
- Expands the instant navs fixture and tests to cover SPA captures, MPA
captures, reloads, close/reset, Continue Rendering, and root-layout MPA
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