Add `PrimMonad` instance for the strict `SamplerT` #608

Job	Run time
lint	32s
build (ubuntu-latest, x86_64-linux)	2m 13s
build-all-ghcs (ghc902)	4m 54s
build (macos-latest, x86_64-darwin)	4m 23s
build-all-ghcs (ghc927)	3m 46s
build-all-ghcs (ghc945)	3m 46s
build-all-ghcs (ghc964)	3m 46s
build-all-ghcs (ghc982)	3m 54s
build-all-ghcs (ghc9101)	4m 4s
notebooks (ubuntu-latest, x86_64-linux)	4m 13s
	35m 31s

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