Refactor PartitionsSaxHandler to use boost::json #2211

Job	Run time
PSV.iOS.MacOS15.Xcode16.ARM64	6m 46s
PSV.Linux.22.04.gcc9.Cpplint	10s
PSV.Linux.22.04.gcc9.Tests.CodeCov	2m 39s
PSV.Linux.22.04.gcc11.Tests	3m 38s
PSV.Clang.Format.Checker	32s
PSV.Win.VC2022	10m 17s
PSV.Linux.22.04.gcc13.Tests	17s
PSV.iOS.MacOS14.Xcode15.ARM64	7m 56s
PSV.Linux.latest.gcc14.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	2m 45s
PSV.Commit.Checker	7s
PSV.Linux.latest.gcc14.Tests	3m 31s
PSV.Linux.22.04.gcc11.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	3m 14s
PSV.Linux.Android.22.04	7m 37s
PSV.Linux.22.04.clang.Tests	3m 30s
PSV.Linux.22.04.gcc9.OLP_SDK_ENABLE_DEFAULT_CACHE=OFF	3m 24s
PSV.iOS.MacOS15.Xcode26.ARM64	8m 33s
PSV.MacOS15.Xcode16.ARM64	7m 18s
	1h 12m 14s

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