[jfx17u] RFR: 8302294: Cherry-pick WebKit 615.1 stabilization fixes

[Kevin Rushforth]

Clean backport to `jfx17u`. Tested in connection with all other WebKit backports in `jfx-kcr-17.0.7` branch.

-------------

Commit messages:
 - 8302294: Cherry-pick WebKit 615.1 stabilization fixes

Changes: https://git.openjdk.org/jfx17u/pull/125/files
 Webrev: https://webrevs.openjdk.org/?repo=jfx17u&pr=125&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8302294
  Stats: 1797 lines in 198 files changed: 834 ins; 508 del; 455 mod
  Patch: https://git.openjdk.org/jfx17u/pull/125.diff
  Fetch: git fetch https://git.openjdk.org/jfx17u pull/125/head:pull/125

PR: https://git.openjdk.org/jfx17u/pull/125