Reland "[Tab Groups] New AnimationHandler Unit Tests"

This reverts commit 335c5f7723e857a95473bbf2ef9e0a410cb0982d.

Reason for revert: AnimationHandler Unit Tests were affected by issues with other tests.

Original change's description:
> Revert "[Tab Groups] New AnimationHandler Unit Tests"
>
> This reverts commit ead2166fb7d958cee4e2642f50924627488bccd5.
>
> Reason for revert: Bisection found this change to break a couple of tests in the org.chromium.ui.dragdrop.DropDataAndroidUnitTest test suite. crbug.com/383748065
>
> Original change's description:
> > [Tab Groups] New AnimationHandler Unit Tests
> >
> > - Initialize unit tests
> >
> > Bug: 362329064
> > Change-Id: I320983d321b1b8087ab31b0ff56425e288d77f5e
> > Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6089611
> > Reviewed-by: Theresa Sullivan <twellington@chromium.org>
> > Commit-Queue: Fiaz Muhammad <mfiaz@google.com>
> > Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
> > Reviewed-by: Brandon Fong <bjfong@google.com>
> > Cr-Commit-Position: refs/heads/main@{#1395386}
>
> Bug: 362329064
> Bug: 383748065
> Change-Id: I915699d52c4da544b742b908ff9817c704c90559
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6089144
> Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
> Commit-Queue: Ashley Newson <ashleynewson@chromium.org>
> Owners-Override: Ashley Newson <ashleynewson@chromium.org>
> Cr-Commit-Position: refs/heads/main@{#1395461}

Bug: 362329064
Bug: 383748065
Change-Id: Ia1c3e0d26f1ab50ae47e4ef32248ab6aa4297be8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6087833
Commit-Queue: Fiaz Muhammad <mfiaz@google.com>
Reviewed-by: Theresa Sullivan <twellington@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Calder Kitagawa <ckitagawa@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1396074}