Resources extension: TemporaryDirectory: Allow custom parent directory

[jbduncan]

Consider introducing the ability to change where our TemporaryDirectory writes its temporary directories to. Currently it writes all directories to the filesystem path in the java.io.tmpdir system property. Users can adjust the property in their build tool or directly in their tests, but the build tool approach isn't the most flexible, and the direct approach wouldn't allow the affected tests to run in parallel, I'd imagine.

junit-pioneer used to have a TempDirectory class with this ability, but it was removed because the built-in JUnit 5 TempDir was superior in almost every way.

This issue is a follow-up to #348 | #491.

Relevant JUnit 5 issues:

• Provide support for setting a custom parent directory for @TempDir junit-team/junit5#2088

Docs for the old TempDirectory extension: https://github.com/junit-pioneer/junit-pioneer/blob/1415785e909f82066df2bd2b5ccfa10396aab0a0/docs/temp-directory.adoc