feat: pass `resid_prototype` as `u` to null oop `NonlinearLeastSquaresProblem` #311

Job	Run time
Tests (1, Core) / Tests - Core	5m 48s
Tests (1, Downstream) / Tests - Downstream	24m 53s
Tests (1, Downstream2) / Tests - Downstream2	26m 22s
Tests (lts, Core) / Tests - Core	3m 44s
Tests (lts, Downstream) / Tests - Downstream	14m 43s
Tests (lts, Downstream2) / Tests - Downstream2	17m 22s
Tests (pre, Core) / Tests - Core	6m 41s
Tests (pre, Downstream) / Tests - Downstream	56m 13s
Tests (pre, Downstream2) / Tests - Downstream2	56m 19s
	3h 32m 5s

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