refactor!: move preconditioners inside linear solvers #133

Job	Run time
downgrade (1.10, core)	12m 23s
downgrade (1.10, adjoint)	8m 30s
test (1.10, ubuntu-latest, core)	12m 34s
test (1.10, ubuntu-latest, adjoint)	8m 29s
downgrade (1.10, alloc_check)	8m 35s
test (1.10, ubuntu-latest, alloc_check)	8m 51s
test (1.10, macos-latest, core)	13m 59s
test (1.10, macos-latest, adjoint)	6m 34s
test (1.10, macos-latest, alloc_check)	5m 57s
test (1.10, windows-latest, core)	14m 8s
test (1.10, windows-latest, adjoint)	10m 21s
test (1.10, windows-latest, alloc_check)	9m 59s
test (1, ubuntu-latest, core)	21m 50s
test (1, ubuntu-latest, adjoint)	15m 22s
test (1, ubuntu-latest, alloc_check)	14m 43s
test (1, macos-latest, core)	16m 32s
test (1, macos-latest, adjoint)	9m 58s
test (1, macos-latest, alloc_check)	10m 10s
test (1, windows-latest, core)	23m 22s
test (1, windows-latest, adjoint)	17m 49s
test (1, windows-latest, alloc_check)	16m 5s
	4h 26m 11s

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