Feature/pyfdb_integration Porting PyFDB to Pybind 11

[tbkr]

Description

I'm aware that this is a somewhat mid-sized PR 😉 It's also a complete rewrite with tests and documentation.

Porting FDB to PyBind11, making the Python-API more user-friendly and introducing tests for the API layer which are testing core functionality of the FDB in an ephemeral FDB setup.

Documentation is added to the code base as well as the sphinx generated side.

The coverage was tested and is close to 100% testing all provided use-cases and functionalities.

For now I keep this PR in WIP status and I'm open to discuss Implementation details.

Notes for reviewers:

• Think about the current API design and raise issues, esp. if you are aware of use-cases which aren't currently implemented
• Read the documentation carefully and check whether the written functionalities are correctly mirrored from the FDB.
• Feel free to raise potential issues I'm not aware of at this point in time.

Contributor Declaration

By opening this pull request, I affirm the following:

• All authors agree to the Contributor License Agreement.
• The code follows the project's coding standards.
• I have performed self-review and added comments where needed.
• I have added or updated tests to verify that my changes are effective and functional.
• I have run all existing tests and confirmed they pass.

🌈🌦️📖🚧 Documentation FDB 🚧📖🌦️🌈 https://sites.ecmwf.int/docs/dev-section/fdb/pull-requests/PR-193

🌈🌦️📖🚧 Documentation Z3FDB 🚧📖🌦️🌈 https://sites.ecmwf.int/docs/dev-section/z3fdb/pull-requests/PR-193

🐍🌦️📖🚧 Documentation PYFDB 🚧📖🌦️🐍 https://sites.ecmwf.int/docs/dev-section/pyfdb/pull-requests/PR-193

[codecov-commenter]

Codecov Report

:white_check_mark: All modified and coverable lines are covered by tests. :white_check_mark: Project coverage is 72.48%. Comparing base (e2621a3) to head (f4f57ea).

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #193      +/-   ##
===========================================
- Coverage    72.62%   72.48%   -0.15%     
===========================================
  Files          360      360              
  Lines        21705    21705              
  Branches      2244     2242       -2     
===========================================
- Hits         15764    15732      -32     
- Misses        5941     5973      +32     

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