Use per-project pipeline IID for pipeline URLs (routes change)

Description

Currently, pipeline ID is used for pipeline URLs,

e.g.

• https://gitlab.com/gitlab-org/gitlab-ce/pipelines/21621476 (Pipeline detail page)
• https://gitlab.com/gitlab-org/gitlab-ce/pipelines (Pipeline list)

Once we have implemented https://gitlab.com/gitlab-org/gitlab-ce/issues/3691, we can use per-project pipeline IID for those pages. Issues and merge requests have already been using its per-project IID. So it's natural order to use it for pipelines.

Proposal

Use per-project pipeline IID for pipeline URLs (routes change)

Links / references

• https://gitlab.com/gitlab-org/gitlab-ce/issues/3691
• https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/18558#note_70907756

/cc @bikebilly @ayufan