fix: implement some performance improvements

[wolfy1339]

• Pre-compute the keys of the Endpoint type in order to not have to compute them multiple times
• Use interface extends instead of intersections

See https://github.com/microsoft/TypeScript/wiki/Performance
Part of #666

---

Before the change?

• Utilized keyof Endpoint directly in the code many times across different files
• Used intersections for extending types

After the change?

• Pre-compute the keys of the Endpoint type that can be shared across many files
• Utilize interfaces and extends for better performance

Pull request checklist

• Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes
• No

---

[github-actions]

👋 Hi! Thank you for this contribution! Just to let you know, our GitHub SDK team does a round of issue and PR reviews twice a week, every Monday and Friday! We have a process in place for prioritizing and responding to your input. Because you are a part of this community please feel free to comment, add to, or pick up any issues/PRs that are labeled with Status: Up for grabs. You & others like you are the reason all of this works! So thank you & happy coding! 🚀

[MisanthropicBit]

I'll try out this branch in my projects and see if it fixes in the issue in #666 🙂

[wolfy1339]

It should definitely improve things, that's for sure.

When I tested some small test code for Octokit, the TypeScript profiler did identify the hotspot with the keyof Endpoint, other than that there wasn't anything else

[MisanthropicBit]

I tried testing with the branch locally (outside docker) but it seems the issue persists with the same tracing profile as before. I think this PR is still an overall improvement though.