We had similar code in a few places to redirect to the last page if
the given page number is out of range. This unifies the handling in a
new controller concern and adds usage of it in all snippet listings.

Adds frozen string to the following:

* spec/bin/**/*.rb
* spec/config/**/*.rb
* spec/controllers/**/*.rb

xref https://gitlab.com/gitlab-org/gitlab-ce/issues/59758

Re-enables and autocorrects all instances of the
Style/MethodCallWithoutArgsParentheses rule

Updates specs to use new rails5 format.

The old format:
`get :show, { some: params }, { some: headers }`

The new format:
`get :show, params: { some: params }, headers: { some: headers }`

This reverts commit cb10b725c8929b8b4460f89c9d96c773af39ba6b.

Apply the same spam checks to public snippets (either personal snippets
that are public, or public snippets on public projects) as to issues on
public projects.

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/14607.