[css-filters] Move filter-region-transformed-composited-child.html to WPT

This CL migrates filter-region-transformed-composited-child
[-expected].html tests from css3/filters to
external/wpt/css/filter-effects with WPT styles, adding links
to the relevant specs, and test description.

Additionally, this test is renamed to
filter-region-transformed-composited-child-001[-ref].html
to be align with existing test naming style.

Bug: 1063749
Change-Id: Ie6b779978770416df22cf702b377c4d04b207033
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2143021Reviewed-by: Stephen Chenney <schenney@chromium.org>
Commit-Queue: Gyuyoung Kim <gyuyoung@igalia.com>
Cr-Commit-Position: refs/heads/master@{#759141}

third_party/blink/web_tests/css3/filters/filter-region-transformed-composited-child.html → third_party/blink/web_tests/external/wpt/css/filter-effects/filter-region-transformed-composited-child-001.html

+<title>CSS Filters: filtered parent with composited or transformed child</title>
+<link rel="author" title="Stephen White" href="mailto:senorblanco@chromium.org">
+<link rel="help" href="https://drafts.fxtf.org/filter-effects/#FilterProperty">
+<link rel="help" href="https://drafts.fxtf.org/filter-effects/#feComponentTransferElement">
+<link rel="issue" href="https://bugs.chromium.org/p/chromium/issues/detail?id=618642">
+<link rel="issue" href="https://bugs.chromium.org/p/chromium/issues/detail?id=620394">
+<link rel="match" href="reference/filter-region-transformed-composited-child-001-ref.html">
+<meta name="assert" content="This test ensures that filtered parent works correctly with composited or transformed children.">
 <svg xmlns="http://www.w3.org/2000/svg" version="1.1" width="0" height="0">
   <defs>
     <filter id="filter" x="25%" y="0%" width="50%" height="100%">