Add Manage agent policies action

[juliaElastic]

Part of reusable integration policies work.

• Add a new modal Manage agent policies that opens when clicking on agent policies count popover added here Show multiple agent policies on integration policies list UI #182111
• The modal window should display a searchable multiselect component of agent policies (could be reused from the new integration page)
• When agent policies are selected, and the action is submitted, an API request should be made to save the agent policy ids in the integration policy
• The multiselect should display agent policies already linked to the integration
• The action should allow removing existing linkage to agent policies
• When removing an agent policy linkage, a warning should pop up to say “This integration will now be removed from these policies: ” ask the user to agree to proceed or cancel.
• The action should prevent removing the last agent policy linkage until Support integration policies without agent policy references #182220 is completed
• The minimum privileges required to take the action should be Integrations:All and Fleet: Agent policies:All

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[juliaElastic]

@nimarezainia Updated this issue with a consideration to RBAC:

• The minimum privileges required to take the action should be Integrations:All and Fleet: Agent policies:All

Similarly updated the visibility of Shared column and Agent policies count column to require minimum Integrations:Read and Fleet: Agent policies:Read