Simplify fx infra (#485)

* add --host and --kubeconf to `fx up`
* remove `fx infra list` and `fx infra use`
* put assets into skip dir for golangci

* fix lint issue

* upgrade go-ssh-client to consume the 'Connectable' API, enable more
friendly SSH connection error message

* parse 'host' and 'kubeconf' for `fx list` and `fx down` also

* refactor parse

* clean infra stuff

.golangci.yml

@@ -7,6 +7,8 @@ run:
     - examples
     - api/images
     - test/functions
+    - assets/
+    - bundler/go/assets
 linters:
   enable:
     - goimports