refactor: Single source of truth to know if e2ei should be enabled

[atomrc]

Description

We are currently looking at both the FEATURE.ENABLE_E2EI feature flag and the team setting config to know if we should start the e2ei process.
The way we check for e2ei enable state is not consistent accros the app.

This PR harmonizes the source of truth whether the e2ei feature is enabled or not. it's E2EIHandler.getInstance().isE2EIEnabled() method.

Before (in a e2ei disabled team)

After

Checklist

• PR has been self reviewed by the author;
• Hard-to-understand areas of the code have been commented;
• If it is a core feature, unit tests have been added;