Add landingView query param enabling view focus on launch

[sbuggay]

Summary

Enables a landingView parameter that lets users specify which view to focus on launch.

Test plan

Open fn_fusebox.html?landingView=timeline and verify that the Performance panel is focused once opened.

• 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 following the contribution guide for Meta employees OR contribution guide.
• This commit is React Native-specific and cannot be upstreamed.