Separate pipelines query from vuln findings query

What does this MR do?

This MR is step 1 of improving the performance of the vulnerability findings endpoints on the security dashboards. It sets us up to fetch pipelines in a separate request from fetching vulnerabilities, shortening the time to respond of the vulnerability findings endpoints and reducing the risk of the queries timing out.

• Refactors VulnerabilityFindingsFinder to take pipeline IDs and use them in the query for vulnerability findings
• Moves query for pipelines to the controller actions and the caching classes
• Removes Vulnerable. We are no longer using the methods included in it

Issue: #202183 (closed)

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• [-] Database guides
• Separation of EE specific content

Availability and Testing

• [-] Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• [-] Tested in all supported browsers
• [-] Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• [-] Label as security and @ mention @gitlab-com/gl-security/appsec
• [-] The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• [-] Security reports checked/validated by a reviewer from the AppSec team