add save_pvd method to mesh series

The MR adds a method to allow for saving mesh_series as PVD/VTU.

1. Feature description was added to the changelog
2. Tests covering your feature were added?
3. Any new feature or behaviour change was documented?
4. API-breaking changes documented here

added 1 commit

• a9ceb326 - add tests for write_pvd function

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added 1 commit

• 1029a14f - Revert "[meshlib] remove filepath from Mesh"

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added 1 commit

• b15cc1d4 - fix tests

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added 1 commit

• 2f6e28bc - fix tests

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added 1 commit

• f6b02a16 - fix tests

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added 3 commits

• f5d0406d - add tests for write_pvd function
• 6e626084 - Revert "[meshlib] remove filepath from Mesh"
• 68238896 - introduce mesh indices

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added Feature label

requested review from @TobiasMeisel

assigned to @joergbuchwald

added 6 commits

• 68238896...ab996bd1 - 2 commits from branch ogs/tools:main
• c2b23a41 - add save method to mesh series
• 8bd5ce32 - add tests for write_pvd function
• a76133e2 - Revert "[meshlib] remove filepath from Mesh"
• 16b60466 - introduce mesh indices

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added workflowplease review label

requested review from @FZill