RFR: 8362091: Window title bar should reflect scene color scheme [v2]

[Michael Strauß]

> Currently, the color scheme of a system-decorated stage is as follows:
> * On Windows, the title bar is always light (even if the OS color scheme is dark).
> * On macOS and Linux, the title bar is light or dark depending on the OS color scheme.
> 
> The expected behavior is that the title bar matches the color scheme of the `Scene`.
> If an application doesn't specify a color scheme, the title bar color should match the OS color scheme.
> 
> This PR fixes the behavior for Windows and macOS, but not for Linux (there's no good way to do that).
> Depending on how you look at it, this is either a bug fix or an enhancement.

Michael Strauß has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains two commits:

 - Merge branch 'master' into feature/dark-window-frame
   
   # Conflicts:
   #	modules/javafx.graphics/src/main/native-glass/mac/GlassWindow.m
 - Window decorations adapt to color scheme

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Changes: https://git.openjdk.org/jfx/pull/1845/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1845&range=01
  Stats: 183 lines in 17 files changed: 171 ins; 0 del; 12 mod
  Patch: https://git.openjdk.org/jfx/pull/1845.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1845/head:pull/1845

PR: https://git.openjdk.org/jfx/pull/1845