RFR: 8355740: Update to Xcode 15.4 on macOS

[Kevin Rushforth]

This PR updates the compiler on macOS to Xcode 15.4 (from 14.3.1) to match JDK 25.

I ran a full headless and headful test run, including building media and WebKit. No issues were found.

NOTE: Xcode 15.4 requires macOS 14 Sonoma to build (although it is known to build on macOS 13, which might be useful for developer builds). The generated JavaFX code will run on older versions of macOS.

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Commit messages:
 - Merge branch 'master' into 8355740-xcode-15.4
 - Update GHA Xcode version
 - 8355740: Update to Xcode 15.4 on macOS

Changes: https://git.openjdk.org/jfx/pull/1798/files
  Webrev: https://webrevs.openjdk.org/?repo=jfx&pr=1798&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8355740
  Stats: 8 lines in 3 files changed: 1 ins; 1 del; 6 mod
  Patch: https://git.openjdk.org/jfx/pull/1798.diff
  Fetch: git fetch https://git.openjdk.org/jfx.git pull/1798/head:pull/1798

PR: https://git.openjdk.org/jfx/pull/1798