Moves TrialFESpace update

[jmartfrut]

Moves the update of TrialFESpace and state vector copying outside the inner loop in the staggered solver. This ensures the state is updated only once per outer iteration, which aligns with the intended behavior.

[github-actions]

Benchmark Results (Julia v1)

Time benchmarks

	main	bcb8017...	main / bcb8017...
Constitutive models/Visco-elastic Ψ	0.0502 ± 0.027 ms	0.0505 ± 0.027 ms	0.995 ± 0.76
Constitutive models/Visco-elastic ∂Ψu	0.0663 ± 0.0097 ms	0.0663 ± 0.007 ms	0.999 ± 0.18
Constitutive models/Visco-elastic ∂Ψuu	0.117 ± 0.016 ms	0.115 ± 0.015 ms	1.02 ± 0.19
Simulations/StaticMechanicalDirichlet	0.139 ± 0.0089 s	0.133 ± 0.0087 s	1.05 ± 0.096
Simulations/StaticMechanicalNeumann	0.134 ± 0.014 s	0.132 ± 0.0082 s	1.01 ± 0.12
Simulations/ViscoElastic	21.4 s	20.5 s	1.04
Tensor algebra/Cofactor	0.07 ± 0.01 μs	0.07 ± 0.01 μs	1 ± 0.2
Tensor algebra/Det(A)Inv(A')	0.13 ± 0.01 μs	0.14 ± 0.01 μs	0.929 ± 0.097
Tensor algebra/δδ_λ_2d	30 ± 0 ns	30 ± 0 ns	1 ± 0
Tensor algebra/δδ_μ_2d	30 ± 0 ns	30 ± 0 ns	1 ± 0
time_to_load	2.43 ± 0.049 s	2.35 ± 0.016 s	1.03 ± 0.022

Memory benchmarks

	main	bcb8017...	main / bcb8017...
Constitutive models/Visco-elastic Ψ	1.24 k allocs: 0.0777 MB	1.24 k allocs: 0.0777 MB	1
Constitutive models/Visco-elastic ∂Ψu	1.36 k allocs: 0.0898 MB	1.36 k allocs: 0.0898 MB	1
Constitutive models/Visco-elastic ∂Ψuu	2.32 k allocs: 0.155 MB	2.32 k allocs: 0.155 MB	1
Simulations/StaticMechanicalDirichlet	1.51 M allocs: 0.109 GB	1.51 M allocs: 0.109 GB	1
Simulations/StaticMechanicalNeumann	1.48 M allocs: 0.0933 GB	1.48 M allocs: 0.0933 GB	1
Simulations/ViscoElastic	0.343 G allocs: 22 GB	0.343 G allocs: 22 GB	1
Tensor algebra/Cofactor	1 allocs: 0.0781 kB	1 allocs: 0.0781 kB	1
Tensor algebra/Det(A)Inv(A')	4 allocs: 0.25 kB	4 allocs: 0.25 kB	1
Tensor algebra/δδ_λ_2d	0 allocs: 0 B	0 allocs: 0 B
Tensor algebra/δδ_μ_2d	0 allocs: 0 B	0 allocs: 0 B
time_to_load	0.149 k allocs: 11.1 kB	0.149 k allocs: 11.1 kB	1