CI: run tests on linux/arm64

[srenatus]

Since we've started shipping binaries for that platform (#4254), it would be good to also run tests on it.

Note: the same would be true for windows; but we've skipped running tests there because of too many hardcoded assumptions about file paths in our tests. For linux/arm64, however, that should not be a problem.

The work done on the github workflow in #4254 could serve as an example: we'd run the tests on that platform via docker, using the qemu setup.

[srenatus]

Took a stab at it but don't hesitate ripping this out of my hands of you'd like.

[srenatus]

Due to #4280, we'd have to litter more build tags over the repo to be able to run the unit tests without wasm. I think that's not worth it, let's give linux/arm64 coverage when we're able to run all the things on it, not just a subset.