Introduce qemu to verify all the existing platforms

[ahrtr]

bbolt supports lots of platforms,

• such as amd64, arm/arm64, mipsx, mipsx64, s390x, ppc64, ppc64le etc.
• and Linux, Windows etc.

But we only cover part of them in our workflow CI. We should try to cover all (or most) of them using qemu.

Also refer to:

• https://github.com/etcd-io/bbolt/pull/626#issuecomment-1837475990
• https://github.com/etcd-io/bbolt/issues/577

[ahrtr]

If we want to support any new platform, then we should also verify them in the workflow.