`shell_interact()` is currently not nice to use. If you try to cancel
the socat process, it will also break the nixos test. Furthermore
ptpython creates it's own terminal that subprocesses are running in,
which breaks some of the terminal features of socat.
Hence this commit extends `shell_interact` to allow also to connect to
arbitrary servers i.e. tcp servers started by socat.
A few places used Unicode U+2018/U+2019 left/right single quotes (but
not always correctly balanced). Let's just use plain ASCII single quotes
everywhere.
For example, the wait_for_unit() call in the Moodle test times out for
myself and others[1], so it would be good to be able to increase it to
something less likely to be hit by a test that would otherwise pass.
[1]: https://github.com/NixOS/nixpkgs/pull/177052#issue-1266336706
Without this fix, setting the shellopts in `machine.execute` is
inconsitent. When no timeout is used, shellopts `set -euo pipefail` are
applied to the command as expected. When a timeout is specified, the
shellopts are not applied to the command itself (which is called inside
a `sh -c` that doesn't inherit the shellopts) but rather to the
`timeout` command, leading to the following full command:
```bash
(set -euo pipefail; timeout 900 sh -c 'cmd') | (base64 --wrap 0; echo)\n
```
With this fix, this is the command we get:
```bash
timeout 900 sh -c 'set -euo pipefail; false | true') | (base64 --wrap 0; echo)\n
```
The aarch64-linux versions of the boot.uefiUsb and boot.uefiCdrom tests
were broken by b0fc9da879.
That commit was a refactor which omitted the qemuBinary option, which was
previously available in the legacy start command. This restores that
option and fixes the tests previously mentioned.
