[Testing]: Revive test suite for solid start

[birkskyum]

It would be great for Solid Start to have a test suite again - it's currently entirely disabled, because it's using the legacy solid-start-node, and we need it to use vinxi.

The archived test folder is here:
https://github.com/solidjs/solid-start/tree/main/archived_test

There's an updated harness (the helpers folder) in the vinxi repo that can be reused for solid start

• https://github.com/nksaraf/vinxi/tree/main/test/

This is necessary to join the:

• [Ecosystem CI]: Integration in the vite-ecosystem-ci #1417

[atilafassina]

I think we can close this one since #1719 was merged. We now have a test setup again 🔥