Bug 1939171 [wpt PR 49846] - DOM: Add basic moveBefore() MutationObse…

…rver tests, a=testonly

Automatic update from web-platform-tests
DOM: Add basic moveBefore() MutationObserver tests

See whatwg/dom#1307 (comment).

R=nrosenthalchromium.org

Bug: 40150299
Change-Id: I6be9d91d4e20690694fb20480f0d1d13a766b117
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6108064
Reviewed-by: Noam Rosenthal <nrosenthalchromium.org>
Commit-Queue: Dominic Farolino <domchromium.org>
Cr-Commit-Position: refs/heads/main{#1400321}

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wpt-commits: a53473e775d7da1c4ccb9e67d5b5a3f72e7223b2
wpt-pr: 49846

UltraBlame original commit: f3c0448263a2e25020e8474c519e842535771a93