[jdk17u-dev] RFR: 8299479: Remove metaprogramming/decay.hpp

[George Adams]

prerequisite to bumping googletest to 1.13.0

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Depends on: https://git.openjdk.org/jdk17u-dev/pull/2672

Commit messages:
 - Backport 10a747c70bb957b7dd268009e6062771085b97eb

Changes: https://git.openjdk.org/jdk17u-dev/pull/2675/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=2675&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8299479
  Stats: 103 lines in 3 files changed: 0 ins; 89 del; 14 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/2675.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/2675/head:pull/2675

PR: https://git.openjdk.org/jdk17u-dev/pull/2675