Evaluate and possible improve `TempDir`

The TempDir extension may or may not be thread-safe - it’s hard to say because its tests definitely aren’t (many static fields). The tests need to be made thread-safe, so we can then evaluate the extension itself. Right now, I see no reason why it shouldn’t be possible to make it thread-safe (if it isn’t already).

Also, can we change the name to TemporaryDirectory or something else that doesn’t sound like letters cost actual money?

[nipafx]

The verdict is in, Jupiter’s @TempDir will not get custom FS support. To recapitulate:

• Jupiter and Pioneer both have a @TempDir extension
• both work in essentially the same way (for the user)
• custom file systems is the only thing Pioneer has that Jupiter’s hasn’t
• there are quite a few features that Jupiter has that Pioneer doesn’t
• there are a number of open requests to Jupiter’s feature (see Bish’s list)

Nota bene: @sormuras tried a different approach to the same topic (link, link)

In light of that, here’s my proposal:

• we move forward with the deletion of @TempDir as currently proposed by #327 and close this issue
• we release 1.0
• we create a new one that aims at a larger-picture reevaluation of this feature set, including a closer look at Jupiter’s @TempDir and Christian’s experiments
• we focus on working through currently open PRs, but put that topic on the top of the list right after that

[Bukama]

As I suggest to remove the TempDir months ago because of this, my answer is of course: Yes remove it.