Signed-off-by: NTakuya Noguchi <takninnovationresearch@gmail.com>

Add "smoke" tag to the test

Fix links to views in Page Object files

Review fixes

Remove useless view block

Implement Snippets::Show page object class

Fix review suggestions

Fix review suggestions 2

Fix test with empty snippets state

Remove useless css class

Fix issues

This engine was replaced with CommonMarker in 11.4, it was deprecated
since then.

Rename btn-new, btn-create and btn-save to btn-success
Signed-off-by: NDmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

When a snippet is submitted, but there's an error, we didn't keep the
visibility level. As the default is private, this means that submitting
a public snippet that failed would then fall back to being a private
snippet.

- Some views had a "Close" button. We've removed this, because we don't
  want users accidentally hiding the validation errors and not knowing
  what needs to be fixed.
- Some views used `li`, some used `p`, some used `span`. We've
  standardized on `li`.
- Some views only showed the first error. We've standardized on showing
  all of them.
- Some views added an `#error_explanation` div, which we've made
  standard.

Fixes #2384.