www/qt5-webengine: Manually roll latest commits

Update qtwebengine to [1]
Update submodule qtwebengine-chromium to [2]

Kudos to upstream for keeping on with the Chromium security updates, but the
Chromium submodule doesn't always get updated in the qtwebengine repo. Getting
to the end of the the line for Qt5. This is a custom release based on [1] and
[2], bringing several security fixes and support for Python 3.12 and 3.13.

[1] https://code.qt.io/cgit/qt/qtwebengine.git/commit/?h=5.15&id=9a16262bc87bbf327e988e18c49ab0f47b766fe2
[2] https://code.qt.io/cgit/qt/qtwebengine-chromium.git/commit/?h=87-based&id=480e246dfe9d9dffc3c18585ed53ec51eb8abfbd

Security: a58fdfef-07c6-11f0-8688-4ccc6adda413