Bulk request to backport 12 fixes to 11-dev for 11.0.8

[Kevin Rushforth]

Hi Johan,

I request approval to backport the following 12 fixes to openjfx11:

JDK-8237889: Update libxml2 to version 2.9.10
JDK-8244579: Windows "User Objects" leakage with WebView
JDK-8236832: [macos 10.15] JavaFX Application hangs on video play on 
Catalina
JDK-8240694: [macos 10.15] JavaFX Media hangs on some video files on 
Catalina
JDK-8241629: [macos10.15] Long startup delay playing media over https on 
Catalina
JDK-8242209: Increase web native thread stack size for x86 mode
JDK-8239107: Update libjpeg to version 9d
JDK-8234474: [macos 10.15] Crash in file dialog in sandbox mode
JDK-8236971: [macos] Gestures handled incorrectly due to missing events
JDK-8242530: [macos] Some audio files miss spectrum data when another 
audio file plays first
JDK-8241474: Build failing on Ubuntu 20.04
JDK-8237078: [macOS] Media build broken on XCode 11

-- Kevin