Reland "Updater: Create self-update integration test."

This is a reland of abb75945

Original change's description:
> Updater: Create self-update integration test.
>
> The test is only implemented for mac Chromium-branded
> builds at this time. This is because we haven't yet
> set up imports of Windows or Google-branded code into
> the codebase.
>
> Bug: 1268555
> Change-Id: I4c8e1d9e6edc00cde727d9bedf7285b4588c2def
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3382966


> Auto-Submit: Joshua Pawlicki <waffles@chromium.org>
> Reviewed-by: Sorin Jianu <sorin@chromium.org>
> Commit-Queue: Sorin Jianu <sorin@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#961033}

Bug: 1268555
Change-Id: Ib4ec8afa7e5548715c9fdf729a2fbd7d3d7dc654
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3402642


Reviewed-by: Sorin Jianu <sorin@chromium.org>
Reviewed-by: Xiaoling Bao <xiaolingbao@chromium.org>
Commit-Queue: Joshua Pawlicki <waffles@chromium.org>
Auto-Submit: Joshua Pawlicki <waffles@chromium.org>
Cr-Commit-Position: refs/heads/main@{#961613}