feat: allowing `accept` headers to always be sent through as metadata

[erunion]

🚥 Fix #448

🧰 Changes

• [x] Updates our parameter digestion and analysis to allow Accept headers to always be sent.
• [x] Updates @readme/oas-to-har to fix a quirk where we might prefer non-JSON responses.
  • https://github.com/readmeio/oas-to-har/pull/130
• [x] Removing some dead code from our caching architecture.

🧬 QA & Testing

Provide as much information as you can on how to test what you've done.