Until Qiskit 0.44 via Qiskit/qiskit#10455, in Qiskit docs, methods lived on dedicated HTML pages.

For some reason, when generating the historical API docs for Qiskit, the script failed to generate those method pages and it only generated class pages, module pages, and function pages. So, our redirects from qiskit.org to ibm.com are working properly but resulting in 404s because the method pages are not there.

This would have been caught by #495.

As explained in #543, we intentionally inlined methods/attributes into their class page via the file mergeClassMembers.ts. That in general worked great, but there are a couple of instances where it fails, like https://docs.quantum.ibm.com/api/qiskit/0.33/qiskit.result.Result mentioned in that PR description. We need to figure out why those failed and get them to work consistently.

The other issue was that I did not realize this inlining was happening when setting up redirects from qiskit.org to ibm.com, so we were trying to redirect method pages to non-existent method pages. I have a PR up for review to fix our redirect logic to instead go to the parent class's page.

To close this issue, we need to:

1. Properly inline all methods. That can be verified by running our link checker over these API docs and making sure that all internal links work.
2. Land the redirects change.