fix: issues preventing people from upgrading off our legacy explorer

[erunion]

🧰 What's being changed?

This resolves a handful of issues that are preventing people from upgrading off our legacy API Explorer:

• If we have a language that's technically unsupported by our code snippet generator (like JSON or HTTP), still make an attempt to capitalize the languages name by running it through our common @readme/syntax-highlighter/uppercase method. Without this, there might be a case where a language like JSON ends up in the Explorer's code tab (by way of the manual API editor example) as "json".
• Stop nesting JSON response examples in a double <div className="example example_json">.
• If a legacy response hasn't been fully configured yet, it will have a status code of "" so we should ignore it so as to not render an empty tab in the ResponseExample component.
• If a requestBody had a title or description, we'd retain that text and show some orphan content. (see fix: bug where requestBody title and descriptions would come through oas#160)
• If there was an OAS that was synced into our system that didn't have a servers object (something that could have been possible before we tightened down our OAS validation), we should still try to render the PathUrl for that as @readme/oas-tooling will set the base URL to https://example.com if no server base URL is present.

🗳 Checklist

💡 If answering yes to any of the following, include additional info, before/after links, screenshots, etc. where appropriate!

• 🆕 I'm adding something new!
• 🐛 I'm fixing a bug!
• 📸 I've made some changes to the UI!

[rafegoldberg]

Great to see all this clean up. Code looks good by me.

[rafegoldberg]

👏