[jdk11u-dev] RFR: 8318039: GHA: Bump macOS and Xcode versions

[Antonio Vieiro]

A backport of [JDK-8318039](https://bugs.openjdk.org/browse/JDK-8318039) to update GHA to the newest macos/XCode versions.

This in preparation of  [JDK-8296812](https://bugs.openjdk.org/browse/JDK-8296812) (this is, all macos builds should be failing).

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Commit messages:
 - Backport 605c9767291ddf1c409c3e805ffb3182899d06c2

Changes: https://git.openjdk.org/jdk11u-dev/pull/2835/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk11u-dev&pr=2835&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8318039
  Stats: 6 lines in 3 files changed: 0 ins; 0 del; 6 mod
  Patch: https://git.openjdk.org/jdk11u-dev/pull/2835.diff
  Fetch: git fetch https://git.openjdk.org/jdk11u-dev.git pull/2835/head:pull/2835

PR: https://git.openjdk.org/jdk11u-dev/pull/2835