[jfx11u] RFR: 8283218: Update GStreamer to 1.20.1

[Kevin Rushforth]

Backport to `jfx11u`. Tested in connection with libffi update in the `test-kcr-11.0.16` branch.

This was not a clean backport, but the merge conflicts were trivial to resolve. Here is a summary of the changes. The jfx mainline patch applied cleanly to all other files.

1. The following file is not present in jfx11u, so that part of the patch was skipped:


modules/javafx.media/src/main/native/gstreamer/gstreamer-lite/gst-plugins-good/gst/audioparsers/gstaacparse.c


2. The following files had minor merge conflicts, the first was a diff in surrounding context and the rest were in copyright header blocks:


modules/javafx.media/src/main/native/gstreamer/projects/linux/fxplugins/Makefile
modules/javafx.media/src/main/native/jfxmedia/projects/linux/Makefile
modules/javafx.media/src/tools/native/def-glib.pl
modules/javafx.media/src/tools/native/def-gstlite.pl

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Commit messages:
 - 8283218: Update GStreamer to 1.20.1

Changes: https://git.openjdk.java.net/jfx11u/pull/94/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jfx11u&pr=94&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8283218
  Stats: 38984 lines in 412 files changed: 22060 ins; 5959 del; 10965 mod
  Patch: https://git.openjdk.java.net/jfx11u/pull/94.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx11u pull/94/head:pull/94

PR: https://git.openjdk.java.net/jfx11u/pull/94