Make the file names consistent on "shadow-realm" (i.e. singular, with a
dash).

Bug: v8:11989
Change-Id: Id0a6f417fd9b53b9f7ddf9677da7396fa2481af6
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3606392Reviewed-by: Adam Klein <adamk@chromium.org>
Commit-Queue: Shu-yu Guo <syg@chromium.org>
Cr-Commit-Position: refs/heads/main@{#80164}