[Security Solution] - investigate stopping mounting and unmounting timeline from DOM

[PhilippeOberti]

Description

The Timeline bottom bar isn't currently displayed on every page in Security Solution. Most pages do have it but some don't (like the rules, explore, ml landing pages, the assets page and most of the management pages like endpoints, policies, trusted apps...).

The issue is the way we're showing/hiding Timeline in the UI: we're removing Timeline from the DOM and adding it back, which means we're re-rendering a lot of things unnecessarily.

We should use a different approach to showing/hiding Timeline that is more performant.

Acceptance criteria

• investigate the complexity and feasibility of showing/hiding Timeline in a more efficient way
• if the work seems straightforward, implement the change

[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)