Add DragonFly, illumos, Solaris to CI.

[ncruces]

Hot on the heels of #2338, this adds more OSes using a different action.

The only note compared to the previous one is that, compared to cross-platform-actions/action, vmactions has one action per OS, which is harder to configure, because GitHub doesn't allow matrix runs to configure uses dependencies.

So I had to create a custom action template.yml, and use envsubst to change the uses dependency.

The stretch goal is to, as a follow up, enable the compiler in many of these, confident that it works: https://github.com/ncruces/wazero/pull/3

I also fixed up the README because we're erroneously claiming we test macOS on amd64, but moving to macos-14 runner, we actually test on arm64.