doc: promote `0x` to tier 4

Hey 👋

Context

The diagnostic working group currently works on an initiative to re-evaluate the diagnostic tooling list and its maturity.

Note: it's normally the last batch of updates before closing the issue.

Updated

In the previous instance, we examined the case of the 0x module: issue link.

The tool is widely used in the field and the latest Node.js version is supported. We’ve decided to move it to Tier 4 🎉

But in case you have a different opinion, please share your thoughts in this PR 🙏.

With love ❤️

cc @nodejs/diagnostics