Move NamedArrayPartition back to StartUpDG.jl (temporarily)

[jlchan]

This PR moves NamedArrayPartition back to StartUpDG.

This is done in order to deal with compatibility issues related to trixi-framework/Trixi.jl#1789, which required Trixi to restrict DiffEqBase, which in turn restricts RecursiveArrayTools.jl and prevents us from using version > 3.4.0 (when NamedArrayPartition was moved from StartUpDG.jl).

[codecov]

Codecov Report

Attention: Patch coverage is 94.44444% with 3 lines in your changes missing coverage. Please review.

Project coverage is 95.93%. Comparing base (e011af6) to head (40735e1).

❗ Current head 40735e1 differs from pull request most recent head f8e379d

Please upload reports for the commit f8e379d to get more accurate results.

Files	Patch %	Lines
src/named_array_partition.jl	94.44%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #175      +/-   ##
==========================================
- Coverage   95.96%   95.93%   -0.03%     
==========================================
  Files          27       28       +1     
  Lines        3763     3817      +54     
==========================================
+ Hits         3611     3662      +51     
- Misses        152      155       +3     

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