Since the frontend for this feature isn't ready, better to hide the
confusing field behind a feature flag.

Rails 5 fix Capybara::ElementNotFound: Unable to find visible css #modal-revert-commit and expected: "/bar" got: "/foo"

Closes #44198

https://gitlab.com/gitlab-org/gitlab-ce/issues/23036

Closes #40274

Replaces all the explicit include metadata syntax in the specs (tag:
true) into the implicit one (:tag).
Added a cop to prevent future errors and handle autocorrection.

a reconfirmation

added "Resend confirmation email" for unverified emails

an rspec feature

`allowed_key_types` is removed and the `minimum_<type>_bits` fields are
renamed to `<tech>_key_restriction`. A special sentinel value (`-1`) signifies
that the key type is disabled.

This also feeds through to the UI - checkboxes per key type are out, inline
selection of "forbidden" and "allowed" (i.e., no restrictions) are in.

As with the previous model, unknown key types are disallowed, even if the
underlying ssh daemon happens to support them. The defaults have also been
changed from the lowest known bit size to "no restriction". So if someone
does happen to have a 768-bit RSA key, it will continue to work on upgrade, at
least until the administrator restricts them.

This is an amalgamation of:

* Cory Hinshaw: Initial implementation !5552
* Rémy Coutable: Updates !9350
* Nick Thomas: Resolve conflicts and add ED25519 support !13712

some caused by webkit prefixes

Signed-off-by: Rémy Coutable <remy@rymai.me>