Clean up dashboardDocumentation and securityDashboardHelpPath and update doc links

We have (at least) 4 places that use dashboardDocumentation and securityDashboardHelpPath to link to the docs. We need to do the following:

1. Update the doc links following the table below.

2. Rename dashboardDocumentation and securityDashboardHelpPath to something more descriptive, such as reportUsageHelpPath and notConfiguredHelpPath. We have two docs, one to explain how to set up security scanners to generate vulnerabilities, and another to explain how to use the vulnerability report once the scanners are set up. The variable name should reflect their usage.

3. Use the frontend helpPagePath helper and remove them from the respective helper.rb files: https://gitlab.com/gitlab-org/gitlab/blob/e60f24faf128eab36a89f7e1c93598d49635e936/app/assets/javascripts/helpers/help_page_helper.js

4. Be aware that the link in the "no vulnerabilities" component may need to be different depending on whether we're looking at the vulnerability report or the pipeline security tab.

Description	Doc Link	Screenshot
In the vulnerability report header for project, group, and instance reports	https://docs.gitlab.com/ee/user/application_security/vulnerability_report/
For the "report not configured" component when no pipeline has been run, or no pipeline with a security scan was ever run	https://docs.gitlab.com/ee/user/application_security/configuration/
For the "no vulnerabilities found" component when a pipeline with security scan has been run, but no vulnerabilities were found	https://docs.gitlab.com/ee/user/application_security/configuration/
For the pipeline security report's "no vulnerabilities" found component when a pipeline with security scan has been run, but no vulnerabilities were found (same component as the above one)	https://docs.gitlab.com/ee/user/application_security/configuration/