[jdk21u-dev] RFR: 8280482: Window transparency bug on Linux

[Roland Mesde]

Backporting JDK-8280482: Window transparency bug on Linux.

Problem:
• Windows on screen 0 (default screen) incorrectly lose transparency 
• Only windows on screen 1 should lose transparency
• Root cause: toGlobal() call in checkIfOnNewScreen() doubles the X position, causing wrong screen detection

Solution:
• Remove unnecessary toGlobal() call when passing window bounds to screen detection
• toGlobal() is not required for monitor number checking and causes coordinate miscalculation

Ran GHA Sanity Checks (passed) and related test (passed).

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Commit messages:
 - Backport 0a3c6d6bd010231d02e92016037149e85fb1db3f

Changes: https://git.openjdk.org/jdk21u-dev/pull/2482/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=2482&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8280482
  Stats: 151 lines in 2 files changed: 148 ins; 0 del; 3 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/2482.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/2482/head:pull/2482

PR: https://git.openjdk.org/jdk21u-dev/pull/2482