Rework h5 metadata

[maxnoe]

This is a draft reworking how we deal with the hdf5 metadata.

• To easily identify the "special" metadata fields, these now have a common CTAFIELD prefix
• To follow the same style as the hdf5 table convention, the code now uses the integer position instead of the column name
• As the prefix is stored in the metadata, the HDF5TableReader can now get it from the file metadata and does not have to be provided with prefixes if the mapping from Container field names to column names is unique, an error is raised otherwise.
• The code creating the mapping from column names to container fields was simplified a lot, although it is now more powerful.

I still have to check performance and file size implications of this, and I would want to also address #1944.

This should fix #1971 and #1785

This breaks reading every file produced previously

[nbiederbeck]

I really like this.

[nbiederbeck]

This should also close #1969, I will check my case with this

[codecov]

Codecov Report

Merging #2003 (46a5b3e) into master (93527bf) will increase coverage by 0.02%.
The diff coverage is 98.75%.

@@            Coverage Diff             @@
##           master    #2003      +/-   ##
==========================================
+ Coverage   92.33%   92.35%   +0.02%     
==========================================
  Files         193      193              
  Lines       15708    15794      +86     
==========================================
+ Hits        14504    14587      +83     
- Misses       1204     1207       +3     

Impacted Files	Coverage Δ
ctapipe/conftest.py	94.25% <ø> (ø)
ctapipe/io/datawriter.py	90.09% <ø> (ø)
ctapipe/io/hdf5eventsource.py	90.32% <92.30%> (+0.49%)	⬆️
ctapipe/io/astropy_helpers.py	87.96% <93.33%> (-2.52%)	⬇️
ctapipe/core/container.py	91.12% <100.00%> (+0.08%)	⬆️
ctapipe/io/hdf5tableio.py	95.84% <100.00%> (-0.31%)	⬇️
ctapipe/io/tableio.py	93.39% <100.00%> (ø)
ctapipe/io/tests/test_astropy_helpers.py	100.00% <100.00%> (ø)
ctapipe/io/tests/test_datawriter.py	100.00% <100.00%> (ø)
ctapipe/io/tests/test_hdf5.py	99.66% <100.00%> (+0.03%)	⬆️
... and 2 more

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