Allow for generic DAST count matching

What does this MR do?

Adds method and assertion to match any vulnerability count. Allows for variability in counts as secure determines its process for this.

Note: This does not unquarantine the test. There's a different issue being addressed that will complete unquarantining this test.

• Fixes #36559 (closed)
• Related to #39208 (closed)

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

This should be reconsidered at some point after we've narrowed down how we count vulnerabilities. This generic test allows testing regardless of feature flag setting by reducing specificity.

• [-] Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers

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