Refactor pkg/cidata: avoid y, simplify private func

[alexandear]

The PR refactors code in the pkg/cidata:

• rename y to instConfig;
• pass only necessary params to the setupEnv function.

[jandubois]

Thanks, LGTM

Given recent changes I think the variable should now be called instCfg, but that should probably be done globally in a separate PR.

[jandubois]

Given recent changes I think the variable should now be called instCfg, but that should probably be done globally in a separate PR.

Hmm, there are not that many instance of instConfig or inst.Config, so maybe it can be included in this PR?

$ grep -rc -E 'inst\.?Config' cmd pkg | grep -v :0
cmd/limactl/shell.go:5
cmd/limactl/show-ssh.go:4
pkg/hostagent/hostagent.go:36
pkg/hostagent/inotify.go:1
pkg/hostagent/mount.go:1
pkg/hostagent/requirements.go:5
pkg/instance/ansible.go:1
pkg/instance/create.go:6
pkg/instance/start.go:2
pkg/store/instance.go:1