Adds HGO_4Fibers anisotropic model

[jmartfrut]

Adds the Holzapfel-Gasser-Ogden (HGO_4Fibers) anisotropic hyperelastic constitutive model, and enables composition of mechanical models using the '+' operator.

This commit introduces a new anisotropic hyperelastic material model, HGO_4Fibers, which accounts for the presence of four families of fibers within the material. Additionally, it overloads the '+' operator to allow for easy composition of mechanical models, such as combining isotropic and anisotropic components. This simplifies the creation of complex material behaviors.

[github-actions]

Benchmark Results (Julia v1)

Time benchmarks

	main	fbb23b9...	main / fbb23b9...
Constitutive models/Visco-elastic Ψ	0.047 ± 0.027 ms	0.0471 ± 0.027 ms	0.996 ± 0.81
Constitutive models/Visco-elastic ∂Ψu	0.0606 ± 0.0032 ms	0.0615 ± 0.0038 ms	0.985 ± 0.08
Constitutive models/Visco-elastic ∂Ψuu	0.109 ± 0.014 ms	0.11 ± 0.015 ms	0.986 ± 0.18
Simulations/ViscoElastic	0.0455 h	0.0463 h	0.981
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 ± 0.0039 s	2.45 ± 0.025 s	0.994 ± 0.01

Memory benchmarks

	main	fbb23b9...	main / fbb23b9...
Constitutive models/Visco-elastic Ψ	1.24 k allocs: 0.0782 MB	1.24 k allocs: 0.0782 MB	1
Constitutive models/Visco-elastic ∂Ψu	1.36 k allocs: 0.0904 MB	1.36 k allocs: 0.0904 MB	1
Constitutive models/Visco-elastic ∂Ψuu	2.31 k allocs: 0.155 MB	2.31 k allocs: 0.155 MB	1
Simulations/ViscoElastic	2.72 G allocs: 192 GB	2.72 G allocs: 192 GB	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