[jfx21u] RFR: 8340322: Update WebKit to 620.1

[Johan Vos]

Almost clean backport of JDK-8340322
Manually changed:
* modules/javafx.web/src/main/native/Source/WebCore/html/parser/HTMLElementStack.cpp because JDK-8344899 is not backported
* modules/javafx.web/src/test/java/test/javafx/scene/web/CanvasTest.java because JDK-8339515 is not backported

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Commit messages:
 - Backport 1e6915738d654e6cf7a547e47b8b020117db6bc3

Changes: https://git.openjdk.org/jfx21u/pull/92/files
  Webrev: Webrev is not available because diff is too large
  Issue: https://bugs.openjdk.org/browse/JDK-8340322
  Stats: 773680 lines in 8156 files changed: 644442 ins; 72180 del; 57058 mod
  Patch: https://git.openjdk.org/jfx21u/pull/92.diff
  Fetch: git fetch https://git.openjdk.org/jfx21u.git pull/92/head:pull/92

PR: https://git.openjdk.org/jfx21u/pull/92