Revert "Revert "Extended NothingBC and MultiFieldBC""

[miguelmaso]

Reverts #69

Re-extending again the signature of NothingBC

[github-actions]

Benchmark Results (Julia v1)

Time benchmarks

	main	a919d6b...	main / a919d6b...
Constitutive models/Visco-elastic Ψ	0.0487 ± 0.028 ms	0.0482 ± 0.028 ms	1.01 ± 0.82
Constitutive models/Visco-elastic ∂Ψu	0.0645 ± 0.0064 ms	0.0631 ± 0.006 ms	1.02 ± 0.14
Constitutive models/Visco-elastic ∂Ψuu	0.112 ± 0.015 ms	0.112 ± 0.015 ms	1 ± 0.2
Simulations/StaticMechanicalDirichlet	0.154 ± 0.0073 s	0.156 ± 0.0088 s	0.988 ± 0.073
Simulations/StaticMechanicalNeumann	0.13 ± 0.013 s	0.129 ± 0.011 s	1.01 ± 0.13
Simulations/ViscoElastic	8.25 s	8.19 s	1.01
Tensor algebra/Cofactor	0.07 ± 0 μs	0.07 ± 0.001 μs	1 ± 0.014
Tensor algebra/Det(A)Inv(A')	0.13 ± 0.001 μs	0.14 ± 0.01 μs	0.929 ± 0.067
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	2.37 ± 0.0075 s	2.38 ± 0.031 s	0.997 ± 0.013

Memory benchmarks

	main	a919d6b...	main / a919d6b...
Constitutive models/Visco-elastic Ψ	1.25 k allocs: 0.0794 MB	1.25 k allocs: 0.0794 MB	1
Constitutive models/Visco-elastic ∂Ψu	1.37 k allocs: 0.0917 MB	1.37 k allocs: 0.0917 MB	1
Constitutive models/Visco-elastic ∂Ψuu	2.31 k allocs: 0.158 MB	2.31 k allocs: 0.158 MB	1
Simulations/StaticMechanicalDirichlet	1.7 M allocs: 0.118 GB	1.7 M allocs: 0.118 GB	1
Simulations/StaticMechanicalNeumann	1.43 M allocs: 0.0908 GB	1.43 M allocs: 0.0908 GB	1
Simulations/ViscoElastic	0.128 G allocs: 8.32 GB	0.128 G allocs: 8.32 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