[Security Solution] - investigate stopping rendering all tabs in timeline

[PhilippeOberti]

Description

Over the last few months/years we've seen a lot of SDHs and issues related to the fact that timeline always renders all the tabs even when it's not open. As soon as the timeline bottom bar is present on a page, even if timeline modal isn't open, we're making calls to the server side to fetch whatever is in the timeline tabs.

The reason behind implementing this in the first place was to have the data already fetched by the time a user would open the timeline modal, hence making the UI much nice as it would avoid loading spinners and show the data immediately.

One of the downsides is we're making potentially many calls on many pages even tough the users never opens the timeline modal. Back in December 2023/January 2024, we had a pretty big issue related to the new-at-the-time ESQL tab that was happening because the tab was rendered despite not being visited.

This behavior combined with the fact that timeline is unmounted from and remounted to the DOM every time the user changes to a page that does and does not have timeline in it, makes this even more of a load on the server and UI.

Acceptance criteria

• Investigate the feasibility and the advantages/inconvenients of removing the behavior where all tabs are always rendered
• if no downsides and the work seems straightforward, implement the change

[elasticmachine]

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

[elasticmachine]

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

[elasticmachine]

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