CrOS Settings: Convert multidevice task continuation item browser test
to TS

Additionally, moved the test under the `multidevice_page/` folder to
mirror the app folder structure.

gtest_filter="*MultidevicePageMultideviceTaskContinuationItem*"

Bug: b/270728282
Test: browser_tests --
Change-Id: I331d4e9669cb564ad2f43a529ac50e315f851c38
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4473207
Commit-Queue: Ruma Kesh <rkesh@google.com>
Reviewed-by: Wes Okuhara <wesokuhara@google.com>
Cr-Commit-Position: refs/heads/main@{#1135502}