Check BCs for periodicity for periodic Tree & Structured meshes

[DanielDoehring]

Motivated by #752

This puts out warnings if a mesh with periodic boundaries is used, but still BCs are supplied.
The converse case, where a non-periodic mesh and periodic BCs are paired returns an error, so no additional treatment is added here.

[github-actions]

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[codecov]

Codecov Report

Attention: Patch coverage is 96.15385% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 96.30%. Comparing base (4bf61a0) to head (2b47577).

Files	Patch %	Lines
src/meshes/tree_mesh.jl	50.00%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1860      +/-   ##
==========================================
- Coverage   96.30%   96.30%   -0.00%     
==========================================
  Files         438      438              
  Lines       35577    35603      +26     
==========================================
+ Hits        34259    34284      +25     
- Misses       1318     1319       +1     

Flag	Coverage Δ
unittests	96.30% <96.15%> (-<0.01%)	⬇️

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[ranocha]

Thanks