Add WeakValueHashMap class #3628

Job	Run time
Linux -> Pre-checks	19s
Linux -> Clang-x64, Debug	10m 48s
Linux -> Clang-x64, Release	12m 51s
Linux -> GCC-x64, Release	11m 1s
Linux -> Clang-NO_GLSLANG-NO_HLSL-x64, Release	6m 45s
Linux -> Clang-NO_GLSLANG-x64, Debug	8m 0s
Linux -> GCC-x64, Debug	12m 54s
	1h 2m 38s

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