feat: restore Performance landing page

[hoxyq]

Summary

Restores the legacy landing page that was removed from the upstream in ChromeDevTools@d0ba98e.

We should revisit this decision in the future when we would be able to show at least some live metrics.

Test plan

Before	After

• 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.

[motiz88]

LGTM. I wonder if there's a way to better preserve the history of the original landing page code. (Also, very silly nit: I don't thing this is a "chore" commit as it includes actual functional changes.)

[hoxyq]

I wonder if there's a way to better preserve the history of the original landing page code.

Probably? I am not sure, maybe partially reverting the original change and then modifying / renaming the file.

But since this file was removed, there should be no conflicts in the future, because this is RN-only. I am just expecting that whoever is going to stop by this file would open blame and read this PR, which has some context.