RFR: 8337400: [Linux] Initial window position is not centered on Ubuntu 24.04 / Xorg

[Thiago Milczarek Sayao]

On Ubuntu 24.04 with Xorg windows are not shown centered.

This is due a configure event being received with position 0,0 which is wrong.

The fix ignores the configure events until the window is mapped.

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Commit messages:
 - 8337400: [Linux] Initial window position is not centered on Ubuntu 24.04 / Xorg

Changes: https://git.openjdk.org/jfx/pull/1520/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1520&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8337400
  Stats: 15 lines in 3 files changed: 14 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jfx/pull/1520.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1520/head:pull/1520

PR: https://git.openjdk.org/jfx/pull/1520