Refactor PartitionsSaxHandler to use boost::json #2212

Job	Run time
PSV.Linux.latest.gcc14.Tests	3m 38s
PSV.Linux.latest.gcc14.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	2m 45s
PSV.Linux.22.04.gcc9.Cpplint	10s
PSV.Linux.22.04.gcc9.Tests.CodeCov	3m 7s
PSV.Linux.22.04.gcc9.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	2m 51s
PSV.Linux.22.04.gcc11.Tests	3m 50s
PSV.MacOS15.Xcode16.ARM64	10m 27s
PSV.iOS.MacOS15.Xcode26.ARM64	7m 9s
PSV.Linux.22.04.clang.Tests	3m 49s
PSV.iOS.MacOS14.Xcode15.ARM64	8m 5s
PSV.Linux.Android.22.04	8m 44s
PSV.iOS.MacOS15.Xcode16.ARM64	5m 40s
PSV.Clang.Format.Checker	37s
PSV.Commit.Checker	7s
PSV.Win.VC2022	10m 17s
PSV.Linux.22.04.gcc13.Tests	22s
PSV.Linux.22.04.gcc11.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	3m 5s
	1h 14m 43s

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