Add morph() for JAX-based Material

[adtzlr]

This PR adds the MORPH material formulation for a JAX-based material. It is about 6x faster compared to the tensortrax-implementation with a more numpy-like experience.

import felupe as fem

umat = fem.constitution.autodiff.jax.Material(
    fem.constitution.autodiff.jax.models.lagrange.morph,
    p=[0.039, 0.371, 0.174, 2.41, 0.0094, 6.84, 5.65, 0.244],
    nstatevars=13,
)
mesh = fem.Cube(n=2)
region = fem.RegionHexahedron(mesh)
field = fem.FieldContainer([fem.Field(region, dim=3)])

boundaries, loadcase = fem.dof.uniaxial(field, clamped=True)
solid = fem.SolidBody(umat=umat, field=field)

move = fem.math.linsteps([0, 1], num=3)
ramp = {boundaries["move"]: move}
step = fem.Step(items=[solid], ramp=ramp, boundaries=boundaries)
job = fem.Job(steps=[step])
job.evaluate(tol=1e-4)

[adtzlr]

remove Python 3.8 support (EOL), see #863

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 97.62%. Comparing base (b87862a) to head (06eaffc).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #880      +/-   ##
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+ Coverage   97.60%   97.62%   +0.01%     
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  Files         154      157       +3     
  Lines        5888     5928      +40     
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+ Hits         5747     5787      +40     
  Misses        141      141              

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