#688: Move utils_instance_or_reference_wrapper.hpp to `solvers_nonlinear` #306

Job	Run time
baseline (fedora-clang-17, Release)	12m 14s
baseline (fedora-clang-17, Debug)	9m 13s
baseline (fedora-gnu-13, Release)	11m 1s
baseline (fedora-gnu-13, Debug)	9m 5s
baseline (ubuntu-clang-14, Release)	11m 58s
baseline (ubuntu-clang-14, Debug)	8m 55s
baseline (ubuntu-gnu-11, Release)	10m 20s
baseline (ubuntu-gnu-11, Debug)	9m 35s
baseline (ubuntu-gnu-11, Release, -D CMAKE_CXX_STANDARD=20 -D PRESSIO_ENABLE_CXX20=ON)	11m 12s
baseline (ubuntu-clang-14, Release, -D CMAKE_CXX_STANDARD=20 -D PRESSIO_ENABLE_CXX20=ON)	13m 1s
baseline (fedora-gnu-13, Release, -D CMAKE_CXX_STANDARD=20 -D PRESSIO_ENABLE_CXX20=ON)	13m 2s
baseline (fedora-clang-17, Release, -D CMAKE_CXX_STANDARD=20 -D PRESSIO_ENABLE_CXX20=ON)	13m 31s
	2h 13m 7s

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