Rename btn-new, btn-create and btn-save to btn-success

Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>

Signed-off-by: Tao Wang <twang2218@gmail.com>

Closes #36459

fixed some more breadcrumb titles

[ci skip]

Also moves action buttons into the new breadcrumbs

Closes #34030, #34033

https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/1210 disabled
autocomplete for personal snippets and project snippets. But we want
autocomplete on project snippets.

Fix https://gitlab.com/gitlab-org/gitlab-ce/issues/33594

Was supposedly fixed in MR for
https://gitlab.com/gitlab-org/gitlab-ce/issues/32086 but seeing this pop
up again

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.

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.