Add "Manage integrations" as a customizable permission

Proposed Permission

Group and project maintainers have the ability to manage integrations. This often leads to a user who is overprivileged where they may not need other group or project destructive permissions. With the release of this permission, you can create a custom role and set the permission to enable least privileged access.

Proposal and User Experience

Group Actions	Project Actions
Integrations List Create/Edit Integration	Integrations List Create/Edit Integration

Views+Workflows include:

• Base + Permission: Group → Settings → Integrations
• Base + Permission: Project → Settings → Integrations
• Base + Permission: Integration -> Edit (settings/integrations/[integration]/edit

Impacted APIs

• https://docs.gitlab.com/ee/api/integrations.html

Documentation

• Permission Title: "Manage integrations"
• Permission Description: "Create, read, update, and delete integrations with external applications."
• Update prerequisites for feature documentation. Include links to feature pages.