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The CombinedLCG is a terrible RNG with a questionable API and should ideally not be used anymore. While in the case of ext/session it is only used for probabilistic garbage collection where the quality of the RNG is not of particular importance, there are better choices. Replace the RNG used for garbage collection by an ext/session specific instance of PcgOneseq128XslRr64. Its 16 Byte state nicely fits into the memory freed up by the previous reordering of the session globals struct, even allowing to the storage of the php_random_algo_with_state struct, making using the RNG a little nicer. Instead multiplying the float returned by the CombinedLCG by the GC Divisor to obtain an integer between 0 and the divisor we can just use `php_random_range` to directly generate an appropriate integer, completely avoiding the floating point maths, making it easier to verify the code for correctness.