Revert "improve type stabitity of jacobian!"

[ChrisRackauckas]

Reverts #2836 @oscardssmith tests seem to do something funky with it (LTS doesn't use sources, and something happened with the others due to a caching issue in the local machines 😅) let's just do the other fix.

[github-actions]

Benchmark Results (Julia v1)

Time benchmarks

	master	45b02b8...	master / 45b02b8...
construction/linear_N50	27.9 ± 13 μs	28.1 ± 14 μs	0.99 ± 0.67
construction/lotka_volterra	19.1 ± 0.27 μs	18.9 ± 0.19 μs	1.01 ± 0.018
construction/rober	18.9 ± 0.19 μs	19 ± 0.18 μs	0.993 ± 0.014
nonstiff/fitzhugh_nagumo/BS3	0.146 ± 0.0098 ms	0.144 ± 0.0099 ms	1.01 ± 0.097
nonstiff/fitzhugh_nagumo/DP5	0.0974 ± 0.0095 ms	0.0969 ± 0.0098 ms	1 ± 0.14
nonstiff/fitzhugh_nagumo/Tsit5	0.116 ± 0.0085 ms	0.117 ± 0.0081 ms	0.993 ± 0.1
nonstiff/fitzhugh_nagumo/Vern6	0.169 ± 0.0085 ms	0.169 ± 0.0088 ms	0.998 ± 0.072
nonstiff/fitzhugh_nagumo/Vern7	0.114 ± 0.0085 ms	0.114 ± 0.0081 ms	0.998 ± 0.1
nonstiff/lotka_volterra/BS3	0.289 ± 0.011 ms	0.296 ± 0.011 ms	0.977 ± 0.05
nonstiff/lotka_volterra/DP5	0.0471 ± 0.017 ms	0.0471 ± 0.017 ms	1 ± 0.52
nonstiff/lotka_volterra/Tsit5	0.0633 ± 0.026 ms	0.0632 ± 0.023 ms	1 ± 0.54
nonstiff/lotka_volterra/Vern6	0.0814 ± 0.011 ms	0.0816 ± 0.011 ms	0.997 ± 0.18
nonstiff/lotka_volterra/Vern7	0.0607 ± 0.022 ms	0.0491 ± 0.022 ms	1.23 ± 0.7
nonstiff/pleiades/BS3	0.087 ± 0.02 s	0.0876 ± 0.012 s	0.993 ± 0.27
nonstiff/pleiades/DP5	1.24 ± 0.073 ms	1.32 ± 0.11 ms	0.938 ± 0.093
nonstiff/pleiades/Tsit5	15.4 ± 4.9 ms	15.4 ± 5.1 ms	1 ± 0.46
nonstiff/pleiades/Vern6	7 s	7.39 s	0.947
nonstiff/pleiades/Vern7	7.83 s	7.84 s	0.998
scaling/brusselator_2d/16x16	0.302 ± 0.02 s	0.304 ± 0.0085 s	0.995 ± 0.071
scaling/brusselator_2d/32x32	7.11 s	7.22 s	0.984
scaling/brusselator_2d/8x8	11.2 ± 0.19 ms	11.2 ± 0.24 ms	0.996 ± 0.027
scaling/linear/N10	0.037 ± 0.017 ms	0.037 ± 0.017 ms	1 ± 0.65
scaling/linear/N100	0.794 ± 0.019 ms	0.792 ± 0.019 ms	1 ± 0.033
scaling/linear/N50	0.213 ± 0.012 ms	0.212 ± 0.011 ms	1 ± 0.078
stiff/pollution/FBDF	0.588 ± 0.014 ms	0.591 ± 0.014 ms	0.996 ± 0.034
stiff/pollution/KenCarp4	0.547 ± 0.011 ms	0.551 ± 0.01 ms	0.993 ± 0.027
stiff/pollution/Rodas4	0.77 ± 0.018 ms	0.784 ± 0.015 ms	0.983 ± 0.03
stiff/pollution/Rosenbrock23	1.34 ± 0.037 ms	1.34 ± 0.034 ms	1 ± 0.038
stiff/pollution/TRBDF2	0.512 ± 0.012 ms	0.514 ± 0.011 ms	0.997 ± 0.032
stiff/rober/FBDF	0.602 ± 0.011 ms	0.607 ± 0.01 ms	0.992 ± 0.024
stiff/rober/KenCarp4	0.745 ± 0.019 ms	0.747 ± 0.019 ms	0.998 ± 0.036
stiff/rober/Rodas4	0.397 ± 0.01 ms	0.396 ± 0.01 ms	1 ± 0.036
stiff/rober/Rosenbrock23	0.267 ± 0.0094 ms	0.266 ± 0.0096 ms	1.01 ± 0.051
stiff/rober/TRBDF2	1.73 ± 0.013 ms	1.71 ± 0.015 ms	1.01 ± 0.012
stiff/van_der_pol/FBDF	9.84 ± 0.079 ms	9.81 ± 0.082 ms	1 ± 0.012
stiff/van_der_pol/KenCarp4	4.75 ± 0.064 ms	4.91 ± 0.053 ms	0.968 ± 0.017
stiff/van_der_pol/Rodas4	7.28 ± 0.052 ms	7.33 ± 0.047 ms	0.993 ± 0.0095
stiff/van_der_pol/Rosenbrock23	20.5 ± 0.16 ms	20.4 ± 0.17 ms	1.01 ± 0.012
stiff/van_der_pol/TRBDF2	2.97 ± 0.069 ms	2.95 ± 0.067 ms	1.01 ± 0.033
time_to_load	3.06 ± 0.021 s	3.07 ± 0.071 s	0.999 ± 0.024

Memory benchmarks

	master	45b02b8...	master / 45b02b8...
construction/linear_N50	0.071 k allocs: 0.0411 MB	0.071 k allocs: 0.0411 MB	1
construction/lotka_volterra	0.065 k allocs: 2.45 kB	0.065 k allocs: 2.45 kB	1
construction/rober	0.065 k allocs: 2.42 kB	0.065 k allocs: 2.42 kB	1
nonstiff/fitzhugh_nagumo/BS3	3.69 k allocs: 0.164 MB	3.69 k allocs: 0.164 MB	1
nonstiff/fitzhugh_nagumo/DP5	2.63 k allocs: 0.127 MB	2.63 k allocs: 0.127 MB	1
nonstiff/fitzhugh_nagumo/Tsit5	4 k allocs: 0.182 MB	4 k allocs: 0.182 MB	1
nonstiff/fitzhugh_nagumo/Vern6	4.54 k allocs: 0.207 MB	4.54 k allocs: 0.207 MB	1
nonstiff/fitzhugh_nagumo/Vern7	3.91 k allocs: 0.165 MB	3.91 k allocs: 0.165 MB	1
nonstiff/lotka_volterra/BS3	7.88 k allocs: 0.365 MB	7.88 k allocs: 0.365 MB	1
nonstiff/lotka_volterra/DP5	1.21 k allocs: 0.0543 MB	1.21 k allocs: 0.0543 MB	1
nonstiff/lotka_volterra/Tsit5	2.17 k allocs: 0.093 MB	2.17 k allocs: 0.093 MB	1
nonstiff/lotka_volterra/Vern6	2.24 k allocs: 0.0986 MB	2.24 k allocs: 0.0986 MB	1
nonstiff/lotka_volterra/Vern7	1.65 k allocs: 0.0736 MB	1.65 k allocs: 0.0736 MB	1
nonstiff/pleiades/BS3	0.685 M allocs: 0.0675 GB	0.685 M allocs: 0.0675 GB	1
nonstiff/pleiades/DP5	6.63 k allocs: 0.51 MB	6.63 k allocs: 0.51 MB	1
nonstiff/pleiades/Tsit5	0.186 M allocs: 20.4 MB	0.186 M allocs: 20.4 MB	1
nonstiff/pleiades/Vern6	0.038 G allocs: 4.05 GB	0.038 G allocs: 4.05 GB	1
nonstiff/pleiades/Vern7	0.044 G allocs: 4.63 GB	0.044 G allocs: 4.63 GB	1
scaling/brusselator_2d/16x16	3.57 k allocs: 0.152 GB	3.57 k allocs: 0.152 GB	1
scaling/brusselator_2d/32x32	3.39 k allocs: 2.22 GB	3.39 k allocs: 2.22 GB	1
scaling/brusselator_2d/8x8	2.62 k allocs: 8.76 MB	2.62 k allocs: 8.76 MB	1
scaling/linear/N10	0.752 k allocs: 0.0514 MB	0.752 k allocs: 0.0514 MB	1
scaling/linear/N100	2.27 k allocs: 0.901 MB	2.27 k allocs: 0.901 MB	1
scaling/linear/N50	1.66 k allocs: 0.348 MB	1.66 k allocs: 0.348 MB	1
stiff/pollution/FBDF	1.5 k allocs: 0.288 MB	1.5 k allocs: 0.288 MB	1
stiff/pollution/KenCarp4	0.508 k allocs: 0.134 MB	0.508 k allocs: 0.134 MB	1
stiff/pollution/Rodas4	1.2 k allocs: 0.36 MB	1.2 k allocs: 0.36 MB	1
stiff/pollution/Rosenbrock23	2.58 k allocs: 0.814 MB	2.58 k allocs: 0.814 MB	1
stiff/pollution/TRBDF2	0.779 k allocs: 0.168 MB	0.779 k allocs: 0.168 MB	1
stiff/rober/FBDF	2.88 k allocs: 0.137 MB	2.88 k allocs: 0.137 MB	1
stiff/rober/KenCarp4	1.29 k allocs: 0.0571 MB	1.29 k allocs: 0.0571 MB	1
stiff/rober/Rodas4	1.96 k allocs: 0.0989 MB	1.96 k allocs: 0.0989 MB	1
stiff/rober/Rosenbrock23	2.24 k allocs: 0.109 MB	2.24 k allocs: 0.109 MB	1
stiff/rober/TRBDF2	7.71 k allocs: 0.36 MB	7.71 k allocs: 0.36 MB	1
stiff/van_der_pol/FBDF	0.0444 M allocs: 2.2 MB	0.0444 M allocs: 2.2 MB	1
stiff/van_der_pol/KenCarp4	3.91 k allocs: 0.173 MB	3.91 k allocs: 0.173 MB	1
stiff/van_der_pol/Rodas4	0.0335 M allocs: 1.73 MB	0.0335 M allocs: 1.73 MB	1
stiff/van_der_pol/Rosenbrock23	0.189 M allocs: 8.37 MB	0.189 M allocs: 8.37 MB	1
stiff/van_der_pol/TRBDF2	4.64 k allocs: 0.201 MB	4.64 k allocs: 0.201 MB	1
time_to_load	0.159 k allocs: 11.2 kB	0.159 k allocs: 11.2 kB	1