Access solution at arbitrary vector of times

[m-bossart]

Expands the interface to allow for passing a vector of times instead of simply a fixed dt or nothing which returns the solution timesteps.

[github-actions]

Performance Results

Version	Precompile Time
Main	2.010416449
This Branch	2.093336906

Version	Run Time
Main-Build ResidualModel	7.615302268
Main-Execute ResidualModel	19.276766833
Main-Build MassMatrixModel	0.953146199
Main-Execute MassMatrixModel	31.553906815
This Branch-Build ResidualModel	6.750129131
This Branch-Execute ResidualModel	19.786375174
This Branch-Build MassMatrixModel	0.610223887
This Branch-Execute MassMatrixModel	31.742519336

ResidualModel and MassMatrixModel performance results should be compared between versions and not between models due to the execution order of the tests

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (10c54fa) 86.99% compared to head (878528c) 87.39%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #365      +/-   ##
==========================================
+ Coverage   86.99%   87.39%   +0.40%     
==========================================
  Files          65       65              
  Lines        9048     9003      -45     
==========================================
- Hits         7871     7868       -3     
+ Misses       1177     1135      -42     

Flag	Coverage Δ
unittests	87.39% <100.00%> (+0.40%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
src/base/simulation_results.jl	68.34% <100.00%> (+0.59%)	⬆️
src/post_processing/post_proc_generator.jl	89.70% <ø> (ø)
src/post_processing/post_proc_inverter.jl	93.38% <100.00%> (ø)
src/post_processing/post_proc_loads.jl	97.19% <ø> (ø)
src/post_processing/post_proc_source.jl	65.00% <ø> (ø)

... and 4 files with indirect coverage changes