www/qt5-webengine: Update to 5.15.2

• Under the hood runs Chromium 83.0.4103.122 with security fixes up to version 86.0.4240.183 and patches were taken from r540991 of www/chromium.

• Also adjust some patches to avoid hardcoding of ${LOCALBASE} and remove a redundant blank line.

Changelog:

• [QTBUG-84632] Warn about QtWebengineProcess launching from network share on Windows.
• [QTBUG-85363] Handle non-ASCII names for PulseAudio
• [QTBUG-85494] Fix regression crash when not handling QQuickWebEngineNewViewRequest
• [QTBUG-85817] Fix crashes on resize
• [QTBUG-86672] Fix remapped menu key being mapped back to menu key
• [QTBUG-86945] Fix crash when opening a PDF in debug build on windows.
• [QTBUG-87129] Mention node.js build-time dependency
• The QtWebEngineProcess now has a version number
• The old compositor has been removed and can no longer be restored using command line argument.

Approved by: tcberner (kde)
Differential Revision: https://reviews.freebsd.org/D27587