[Security Solution][Attacks/Alerts][Attack discovery page] show callout for new Attack page

[PhilippeOberti]

Summary

We need to show a callout component at the top of the Attack discovery page, to reroute users to the new Attacks page

Acceptance criteria

• show callout at the top of the page

[elasticmachine]

Pinging @elastic/security-threat-hunting (Team:Threat Hunting)

[elasticmachine]

Pinging @elastic/security-threat-hunting-investigations (Team:Threat Hunting:Investigations)

[elasticmachine]

Pinging @elastic/security-solution (Team: SecuritySolution)

[e40pud]

Discussed internally and decided that we gonna have only callout on the Attack discovery page.