Revert "Split SigninToUserProfileSwitchTest.LoginAsNewUser into three subtests"

This reverts commit 50601271c4d2d7c4109252dd625bd9b0ecb7e6f9.

Reason for revert: Tests are flaky on linux-chromeos-dbg

See https://crbug.com/1413091 for history

Original change's description:
> Split SigninToUserProfileSwitchTest.LoginAsNewUser into three subtests
>
> Split SigninToUserProfileSwitchTest.LoginAsNewUser into three subtests
> to test spoken feedback during OOBE sign in and log in and after log in.
> Also, removed the tutorial part as it's no longer expected behavior.
>
> This split was necessary to verify spoken feedback in three different
> phases, respectively; otherwise, the test fails due to timed out.
> Ran the tests on Linux 10 times and verified that they all passed.
>
> AX-Relnotes: N/A
> Bug: b:259379912
> Change-Id: Ib5ccf11a43d2903e096e5c1f2032f0665d9b0482
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4220171
> Reviewed-by: Akihiro Ota <akihiroota@chromium.org>
> Commit-Queue: Kyungjun Lee <kyungjunlee@google.com>
> Cr-Commit-Position: refs/heads/main@{#1101064}

Bug: b:259379912
Change-Id: Ia79b5d9cb79ace0e238ad97f1e8b11b079a9d74b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4221060
Commit-Queue: Lingqi Chi <lingqi@chromium.org>
Owners-Override: Lingqi Chi <lingqi@chromium.org>
Quick-Run: Lingqi Chi <lingqi@chromium.org>
Auto-Submit: Lingqi Chi <lingqi@chromium.org>
Commit-Queue: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Cr-Commit-Position: refs/heads/main@{#1101447}