Simpler HybridGaussianFoo constructors #3028

Job	Run time
ubuntu-clang-deprecated Debug	22m 49s
ubuntu-clang-deprecated Release	23m 25s
ubuntu-clang-quaternions Debug	22m 35s
ubuntu-clang-quaternions Release	23m 25s
ubuntu-clang-tbb Debug	23m 39s
ubuntu-clang-tbb Release	22m 58s
ubuntu-clang-cayleymap Debug	22m 55s
ubuntu-clang-cayleymap Release	23m 38s
ubuntu-clang-system-libs Debug	23m 28s
ubuntu-clang-system-libs Release	22m 41s
ubuntu-no-boost Debug	21m 52s
ubuntu-no-boost Release	16m 15s
ubuntu-no-unstable Debug	17m 22s
ubuntu-no-unstable Release	16m 9s
	5h 3m 11s

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