[Fleet] Use react-query to fetch data in agent list page

[nchaulet]

Description

While writing cypress test for the agent list page, when playing with filter quickly it seems that we have some concurent requests to retrieve the agents and the request order is not properly handled.

This cause the table and the status bar to not always render what the user expect, and this will be changed during the next auto refresh of the table (30s later).

This will probably solved by migrating to react-query for these requests.

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)