🐛 fix: Add confirm signature race condition handler

Motivation and context

This PR introduces an enhancement to the beforeMessageSignature method in the Page class. The method now efficiently handles two scenarios: when a scroll button is present on the page and when it's not. This is achieved by using Promise.race() to wait for either the scroll button to become visible and clicked, or for the page to finish loading.

The motivation behind this change is to improve the performance and reliability of the method. Previously, the method could potentially be delayed if the scroll button was not present. With this enhancement, the method will proceed as soon as the relevant condition is met, without any manual delays.

Does it fix any issue?

SYN-83

Other useful info

This enhancement should improve the performance of any operations that involve the beforeMessageSignature method.

Quality checklist

[x] I have performed a self-review of my code.
[x] If it is a core feature, I have added thorough e2e tests.

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Synthetixio / synpress