DAST Pre-scan verification implementation

As a part of configuring scans, users should be able to click a button to verify that:

1. We can connect to the target site.
2. If authentication is specified, we can authenticate to the target site.
3. We are able to follow links and crawl up to 3 pages without errors.

This should be an optional step in any test config and shouldn't interfere with saving the test, even if the verification fails.

Proposal

See the design issue for the approved designs.

1. Add a Pre-scan verification section to the on-demand test config screen.
2. Add a drawer that contains the Pre-scan verification details.
   1. On the test config page
   2. On the On-demand index page
3. Show that the verification process is running.
   1. In the drawer
   2. On the test config page
4. Add alert to on-demand index page when pre-scan verification has finished.
5. Add Pre-scan verification column to Scan Library tab on On-demand index page.
6. Add option on Scan Library page to verify configuration.
7. Show the results of the pre-scan verification in the drawer.

• 📺 Walkthrough video (Note: Some aspects of the design proposal have changed)
• 🕹 Prototype
• 🎨 Figma

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