RFR: Merge jfx:jfx16

[Kevin Rushforth]

Merge jfx16 into master (using Skara tooling). Since there are no merge conflicts, this should not require a review.

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Commit messages:
 - Merge jfx:jfx16
 - 8256362: JavaFX must warn when the javafx.* modules are loaded from the classpath
 - 8259639: GitHub actions: build fails on Linux due to missing apt-get update

The merge commit only contains trivial merges, so no merge-specific webrevs have been generated.

Changes: https://git.openjdk.java.net/jfx/pull/376/files
  Stats: 40 lines in 5 files changed: 40 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jfx/pull/376.diff
  Fetch: git fetch https://git.openjdk.java.net/jfx pull/376/head:pull/376

PR: https://git.openjdk.java.net/jfx/pull/376