Tests were removed in cff6575948 to get rid of yants.
This reimplements a minimal runTestsuite feature set to support the readTree tests.
Fixes https://git.snix.dev/snix/snix/issues/71
Change-Id: I56e6e6e518cbbd6170b11f6d9ee8d62485dcb56e
Reviewed-on: https://cl.snix.dev/c/snix/+/30107
Reviewed-by: Florian Klink <flokli@flokli.de>
Tested-by: besadii
Reviewed-by: adis bladis <adisbladis@gmail.com>