chore: reorganize mocks

[toph-allen]

Most of the mocks are organized into subdirectories by Connect version. The default mock directory is named 2024.08.0 but it actually does not contain a version number in its server settings. The other mock directories do respond like the named Connect version.

Some options:

• At the very least, the default mock directory should be renamed something like unversioned (with a note in a README to describe what that means). This might be fine for tests that use code that doesn't explicitly check the Connect version.
• Another option would be to remove the default mock path and always be explicit (described by @nealrichardson here). Even code that doesn't explicitly check a version of Connect is written against some version, so it might just be good practice to put any mock in a directory for the version of Connect it was captured from.

[nealrichardson]

Another thing to keep in mind: mock paths in httptest work like .libPaths, in that you can stack them up and if a mock isn't found in the first dir, it will check in the next. Since most APIs don't change, we probably want the default (possibly "unversioned") have most things, and then we can set mock paths like c("2025.04.0", "unversioned") to have something work with the new APIs in the right places. For some things that might be overly complicated to reason about, but for simple things where we don't want to have to reproduce a whole bunch of mocks just because a new version of Connect added a new API, it could be helpful.