test: more reliable e2e

[pawelstepien-da]

Improvements to Wallet Gateway E2E tests aimed at reducing flakiness and making debugging easier.

Notable changes to tests:
-Added more assertions after actions, to ensure that they already took effect before proceeding to avoid race conditions or to fail early.
-Merged popup and separate page WG utils into one util with isPopup param.
-Reduced pollings that would make failures make tests take long time waiting for positive outcome that would never come.
-Wrapped test/utils step with test.step, added descriptions to steps and expects for more readable logs.

Notable changes to app logic, that were inducing flakiness, mostly race conditions not/rarely observed in regular usage, because of human speed:
-mock-oauth2 - added random as icp claim, which makes each JWT unique. Before they could be the same, if 2 token were generated in same second for same user and network.
-WG select network screen - submitting is locked until both listNetworks and listIdps requests finish. Before it was possible to click login with only listNetworks finished, while listIdps was still pending which caused UI error.
-WG UI root level component user-app now delays rendering page component for URL, until session verification completes, rendering "Loading..." instead. Before it could cause problems like page executing connectCallback just to be redirected to /login a moment later, or interrupting the session check (i.e. because a page list rendered too fast and test clicked "Add" button, causing a redirtect) resulted getSessionId going to catch which return sessionId null, which resulted in call to attemptRemoveSession - flaky and hard to debug.

[pawelstepien-da]

#1867