Unit tests are no longer run in github actions

[cfergeau]

b525dc8#r1909010646

test-linux is not running as many tests as what test was running, go test ./... was running all of these:

pkg/services/dns/dns_test.go
pkg/services/dns/hosts_file_test.go
pkg/tap/ip_pool_test.go
test-win-sshproxy/basic_test.go
test-win-sshproxy/suite_test.go
test/basic_test.go
test/efi_darwin_arm64_test.go
test/port_forwarding_test.go
test/suite_test.go

Imo we can keep a test target which runs go test ./... but add build tags to the vfkit tests so that they are only run on macos and/or use the -skip parameter together with go test ./... to have more control over what is being run.