Global IORuntime threadpools are not closed in tests, causing a resource leak

[olivierdeckers]

This library uses IORuntime.global for tests, which causes it to never close the threadpools that are created by this global IORuntime. Combined with sbt creating a new classloader for every test run and every submodule, this results in a lot of IORuntimes and threadpools being created and never cleaned up. Eventually, it causes sbt to run of out memory after a number of test runs, especially in projects with many submodules.

I'm not sure what the best approach would be to avoid this issue, as creating a new IORuntime in every test suite will probably slow down running tests?