Steady State Adjoints for Non-Vector Parameters

[avik-pal]

#877 implements quite a few things. I realized it might be better to split it up. This PR implements:

• linsolve_kwargs: which controls the keyword arguments for the internal linear solver
• Parameters to NonlinearProblem can be Arbitrary Structures!
• Added a file containing utilities for non-vector parameters. We will need it anyways for the Gauss Adjoint work!

[codecov]

Codecov Report

Merging #913 (8ccac8b) into master (fde1523) will decrease coverage by 0.03%.
The diff coverage is 62.50%.

@@            Coverage Diff             @@
##           master     #913      +/-   ##
==========================================
- Coverage   61.60%   61.57%   -0.03%     
==========================================
  Files          19       20       +1     
  Lines        4344     4362      +18     
==========================================
+ Hits         2676     2686      +10     
- Misses       1668     1676       +8     

Files	Coverage Δ
src/SciMLSensitivity.jl	100.00% <ø> (ø)
src/steadystate_adjoint.jl	88.13% <85.71%> (ø)
src/derivative_wrappers.jl	90.19% <89.47%> (ø)
src/sensitivity_algorithms.jl	75.90% <50.00%> (-1.88%)	⬇️
src/parameters_handling.jl	25.00% <25.00%> (ø)

... and 1 file with indirect coverage changes

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