tests/inst: Add destructive test framework

tests/inst: Add destructive test framework

This adds infrastructure to the Rust test suite for destructive
tests, and adds a new `transactionality` test which runs
rpm-ostree in a loop (along with `ostree-finalize-staged`) and
repeatedly uses either `kill -9`, `reboot` and  `reboot -ff`.

The main goal here is to flush out any "logic errors".

So far I've validated that this passes a lot of cycles
using
```
$ kola run --qemu-image=fastbuild-fedora-coreos-ostree-qemu.qcow2 ext.ostree.destructive-rs.transactionality --debug --multiply 8 --parallel 4
```
a number of times.