Redirect old Secure docs to new location

What does this MR do?

Add redirects and deprecate old docs. The new location will be doc/user/application_security/ after the discussion inhttps://gitlab.slack.com/archives/C8S0HHM44/p1555059236004200.

In the parenthesis are the comments, if available, for each page.

1. Redirect old docs to their new location
   • Container Scanning
     • ci/examples/container_scanning.md (5) > user/application_security/container_scanning/index.md
     • ci/examples/sast_docker.md (-) > user/application_security/container_scanning/index.md
     • user/project/merge_requests/sast_docker.md (-) > user/application_security/container_scanning/index.md
     • user/project/merge_requests/container_scanning.md (0) > user/application_security/container_scanning/index.md
   • DAST
     • ci/examples/dast.md (0) > user/application_security/dast/index.md
     • user/project/merge_requests/dast.md (0) > user/application_security/dast/index.md
   • Dependency Scanning
     • ci/examples/dependency_scanning.md (1) > user/application_security/dependency_scanning/index.md
     • user/project/merge_requests/dependency_scanning.md (1) > user/application_security/dependency_scanning/index.md
   • Licence Management
     • ci/examples/license_management.md (3) > user/application_security/license_management/index.md
     • user/project/merge_requests/license_management.md (1) > user/application_security/license_management/index.md
   • SAST
     • ci/examples/sast.md (0) > user/application_security/sast/index.md
     • user/project/merge_requests/sast.md (10) > user/application_security/sast/index.md
   • Security Dashboard
     • user/group/security_dashboard/index.md (0) > user/application_security/security_dashboard/index.md
     • user/project/security_dashboard.md (0) > user/application_security/security_dashboard/index.md
2. Find existing occurrences (both in docs and the app) and change the location
3. https://docs.gitlab.com/ee/user/project/merge_requests/#security-reports-ultimate -> link to new location doc/user/application_security/index.md
4. Remove is_hidden
5. Remember to also change the links in the templates https://gitlab.com/gitlab-org/gitlab-ee/tree/master/lib/gitlab/ci/templates/Security
6. After merge, follow https://gitlab.com/gitlab-com/gitlab-docs/issues/357#workflow to merge comments. Use the following CSV:

https://docs.gitlab.com/ee/ci/examples/container_scanning.html, https://docs.gitlab.com/ee/user/application_security/container_scanning/index.html
https://docs.gitlab.com/ee/ci/examples/dependency_scanning.html, https://docs.gitlab.com/ee/user/application_security/dependency_scanning/index.html
https://docs.gitlab.com/ee/user/project/merge_requests/dependency_scanning.html, https://docs.gitlab.com/ee/user/application_security/dependency_scanning/index.html
https://docs.gitlab.com/ee/ci/examples/license_management.html, https://docs.gitlab.com/ee/user/application_security/license_management/index.html
https://docs.gitlab.com/ee/user/project/merge_requests/license_management.html, https://docs.gitlab.com/ee/user/application_security/license_management/index.html
https://docs.gitlab.com/ee/user/project/merge_requests/sast.html, https://docs.gitlab.com/ee/user/application_security/sast/index.html

Related issues

Closes https://gitlab.com/gitlab-org/gitlab-ee/issues/11109

Author's checklist

• Follow the Documentation Guidelines and Style Guide.
• Link docs to and from the higher-level index page, plus other related docs where helpful.
• Apply the ~Documentation label.

Review checklist

All reviewers can help ensure accuracy, clarity, completeness, and adherence to the Documentation Guidelines and Style Guide.

1. Primary Reviewer

• Review by a code reviewer or other selected colleague to confirm accuracy, clarity, and completeness. This can be skipped for minor fixes without substantive content changes.

2. Technical Writer

• Optional: Technical writer review. If not requested for this MR, must be scheduled post-merge. To request for this MR, assign the writer listed for the applicable DevOps stage.

3. Maintainer

1. Review by assigned maintainer, who can always request/require the above reviews. Maintainer's review can occur before or after a technical writer review.
2. Ensure a release milestone is set and that you merge the equivalent EE MR before the CE MR if both exist.
3. If there has not been a technical writer review, create an issue for one using the Doc Review template.