Cleaning up some places where we don't need namedtuples to speed up t…

[cmhamel]

…tfx and simplify types of various structs.

[codecov]

Codecov Report

❌ Patch coverage is 94.44444% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 74.56%. Comparing base (419cc7d) to head (bd20387).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
src/bcs/BoundaryConditions.jl	83.33%	1 Missing ⚠️
src/ics/InitialConditions.jl	92.30%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #203      +/-   ##
==========================================
+ Coverage   73.90%   74.56%   +0.66%     
==========================================
  Files          48       48              
  Lines        2150     2139      -11     
==========================================
+ Hits         1589     1595       +6     
+ Misses        561      544      -17     

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