Feature: t8code cubed spherical shell setups & testing t8code v2.0.0.

[jmark]

This is a follow-PR to https://github.com/trixi-framework/Trixi.jl/pull/1900.

It implements two cubed spherical shell setups and uses the latest t8code v2.0.0 release.

Closes #1921

[github-actions[bot]]

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Created with :heart: by the Trixi.jl community.

[JoshuaLampert]

There are some significant changes in the error values, e.g., here. So basically, elixir_euler_baroclinic_instability.jl doesn't work at all anymore. Do you know what's happening there, @jmark?

[JoshuaLampert]

Ah, I see. This is one of the new elixirs. So looks like there is still some bug somewhere with this elixir.

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 0% with 111 lines in your changes missing coverage. Please review.

Project coverage is 88.68%. Comparing base (f59322c) to head (e9fc20f).

Files	Patch %	Lines
...de_3d_dgsem/elixir_euler_baroclinic_instability.jl	0.00%	98 Missing :warning:
src/meshes/t8code_mesh.jl	0.00%	13 Missing :warning:

Additional details and impacted files

```diff @@ Coverage Diff @@ ## feature-t8codemesh-checkpointing #1918 +/- ## ==================================================================== - Coverage 89.58% 88.68% -0.90% ==================================================================== Files 460 461 +1 Lines 37143 37254 +111 ==================================================================== - Hits 33272 33038 -234 - Misses 3871 4216 +345 ``` | [Flag](https://app.codecov.io/gh/trixi-framework/Trixi.jl/pull/1918/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=trixi-framework) | Coverage Δ | | |---|---|---| | [unittests](https://app.codecov.io/gh/trixi-framework/Trixi.jl/pull/1918/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=trixi-framework) | `88.68% <0.00%> (-0.90%)` | :arrow_down: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=trixi-framework#carryforward-flags-in-the-pull-request-comment) to find out more.

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