Create alert messages for pre-scan verification on-demand scans list

What does this MR do and why?

Describe in detail what your merge request does and why.

This MR resolves #378273 (closed)

This MR adds alert message for on-demand-scans list.

This should work according to this prototype

For now it is static data in alert as backend is in progress. It will be updated with dynamic params for text and variant later.

backend is still in progress, so this MR covers only frontend part for now

Task/issue	MR
Create feature flag / lay groundwork - #376687 (closed)	!100322 (merged)
Create pre-scan verification component - #376690 (closed)	!100593 (merged)
Add drawer for pre-scan verification - #376708 (closed)	!100694 (merged)
Add status summary component to a drawer - #377509 (closed)	!100937 (merged)
Add stepped list for pre-scan verification flow - #377854 (closed)	!101257 (merged)
Add alert message to a sidebar - #378272 (closed)	!102389 (merged)
Add option on Scan Library page - #376705 (closed)	!102290 (merged)
Add pre-scan verification sidebar on Scan Library page - #376705 (closed)	👈🏻 this one

Screenshots or screen recordings

Screenshots are required for UI changes, and strongly recommended for all other merge requests.

BEFORE	AFTER
NO ALERT

How to set up and validate locally

Numbered steps to set up and validate the change are strongly suggested.

1. Enable flag by enabling rails console in terminal

   Feature.enable(:dast_pre_scan_verification)

2. Edit the code to see different states (instructions here)
3. Go to BASE_URL/PROJECT_ID/-/on_demand_scans

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #378273 (closed)