WIP: Sc/Enhanced p4est mesh views

[SimonCan]

Enhance p4est mesh views. Allows for a cell-selection for each view.

[github-actions]

Review checklist

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Purpose and scope

• The PR has a single goal that is clear from the PR title and/or description.
• All code changes represent a single set of modifications that logically belong together.
• No more than 500 lines of code are changed or there is no obvious way to split the PR into multiple PRs.

Code quality

• The code can be understood easily.
• Newly introduced names for variables etc. are self-descriptive and consistent with existing naming conventions.
• There are no redundancies that can be removed by simple modularization/refactoring.
• There are no leftover debug statements or commented code sections.
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Documentation

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• Comments describe intent ("why?") and not just functionality ("what?").
• If the PR introduces a significant change or new feature, it is documented in NEWS.md with its PR number.

Testing

• The PR passes all tests.
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• New or modified tests run in less then 10 seconds.

Performance

• There are no type instabilities or memory allocations in performance-critical parts.
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Verification

• The correctness of the code was verified using appropriate tests.
• If new equations/methods are added, a convergence test has been run and the results
  are posted in the PR.

Created with ❤️ by the Trixi.jl community.

[codecov]

Codecov Report

Attention: Patch coverage is 64.10256% with 42 lines in your changes missing coverage. Please review.

Project coverage is 96.27%. Comparing base (bde0afc) to head (84d22c8).

Files with missing lines	Patch %	Lines
src/solvers/dgsem_p4est/containers_2d.jl	3.70%	26 Missing ⚠️
src/solvers/dgsem_p4est/containers.jl	37.50%	10 Missing ⚠️
src/meshes/p4est_mesh_view.jl	89.83%	6 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2110      +/-   ##
==========================================
- Coverage   96.37%   96.27%   -0.10%     
==========================================
  Files         486      487       +1     
  Lines       39186    39292     +106     
==========================================
+ Hits        37764    37828      +64     
- Misses       1422     1464      +42     

Flag	Coverage Δ
unittests	96.27% <64.10%> (-0.10%)	⬇️

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