[Issue] Initialize authentication popup modal only when needed

[m2-assistant]

This issue is automatically created based on existing pull request: #30647: Initialize authentication popup modal only when needed

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Description (*)

This PR is somehow an evolution of the #27686 in which I have found that it is not possible to completely skip initialization of authentication popup. That said, by adding this additional check, we are able to save a lot of CPU time for all of the shops that have guest checkout enabled.

Here are the profiles of before:

and after:

Manual testing scenarios (*)

1. setModalElement function is no longer called when guest checkout is enabled.
2. Authentication popup still shows properly when guest user tries to go to the checkout but guest checkout is disabled.

Contribution checklist (*)

• Pull request has a meaningful description of its purpose
• All commits are accompanied by meaningful commit messages
• All new or changed code is covered with unit/integration tests (if applicable)
• All automated tests passed successfully (all builds are green)

[m2-assistant]

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