[NOT TO MERGE] Refactor Electro and ThermoElectro models

[miguelmaso]

WIP

model.electro() will replace the function _getCoupling(obj.electro, obj.mechano)

[github-actions]

Benchmark Results (Julia v1)

Time benchmarks

	main	b9361c6...	main / b9361c6...
Constitutive models/Visco-elastic Ψ	0.0457 ± 0.026 ms	0.0431 ± 0.026 ms	1.06 ± 0.89
Constitutive models/Visco-elastic ∂Ψu	0.0488 ± 0.0042 ms	0.0478 ± 0.0038 ms	1.02 ± 0.12
Constitutive models/Visco-elastic ∂Ψuu	0.0873 ± 0.013 ms	0.088 ± 0.018 ms	0.992 ± 0.25
Simulations/StaticMechanicalDirichlet	0.115 ± 0.0075 s	0.118 ± 0.0081 s	0.981 ± 0.093
Simulations/StaticMechanicalNeumann	0.107 ± 0.015 s	0.117 ± 0.011 s	0.918 ± 0.16
Simulations/ViscoElastic	16.4 s	9.77 s	1.68
Tensor algebra/Cofactor	0.06 ± 0 μs	0.06 ± 0.01 μs	1 ± 0.17
Tensor algebra/Det(A)Inv(A')	0.1 ± 0.02 μs	0.1 ± 0.02 μs	1 ± 0.28
Tensor algebra/δδ_λ_2d	20 ± 10 ns	20 ± 10 ns	1 ± 0.71
Tensor algebra/δδ_μ_2d	20 ± 10 ns	20 ± 10 ns	1 ± 0.71
time_to_load	2.37 ± 0.019 s	2.35 ± 0.022 s	1.01 ± 0.012

Memory benchmarks

	main	b9361c6...	main / b9361c6...
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	1.29 k allocs: 0.0826 MB	1.29 k allocs: 0.0826 MB	1
Constitutive models/Visco-elastic ∂Ψuu	2.25 k allocs: 0.149 MB	2.25 k allocs: 0.149 MB	1
Simulations/StaticMechanicalDirichlet	1.51 M allocs: 0.108 GB	1.48 M allocs: 0.113 GB	0.959
Simulations/StaticMechanicalNeumann	1.48 M allocs: 0.0931 GB	1.5 M allocs: 0.102 GB	0.909
Simulations/ViscoElastic	0.327 G allocs: 20.6 GB	0.195 G allocs: 11.8 GB	1.74
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