Changelog: changed

Contributes to https://gitlab.com/gitlab-org/gitlab/-/issues/494689

**Problem**

We are going to add a not null constraint for snippet fields project_id
and organization_id. This change breaks test factories that generate
invalid records without any of these fields.

**Solution**

Update test suite to use a specific snippet type (Project or Personal)
instead of a generic `snippet`.

Checked via:
    - scripts/rspec_check_order_dependence ./spec/views

Changelog: other

Changelog: changed

- Personal or project snippets of banned users will have a spam icon
next to them, with a tooltip letting admins know that these snippets
are hidden from other users because the author of the
snippet has been banned.
- The backend has already been merged and deployed in a
previous milestone.
MR: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/134048

Changelog: added

This reverts merge request !131725

- Create feature-flag hide_snippets_of_banned_users,
which when on will hide snippets created by banned users.
- They will only be visible to admins, with a spam icon
and tooltip to indicate that they have hidden.

Changelog: added