Improve startup time of applications

[GernotMaier]

Applications are very slow in starting up, see issue #681 .

This is mostly related to imports and this pull request is start to optimize this:

• moved hd5-related functions out of utils/general.py into a separate module (io_hdf5)
• for clarity, moved io_handler and io_hdf5 into a new directory simtools.io_operations (most changes of this PR are related to the change of the import statement; note that I have in an earlier version this was simtools.io, but I realised that io is in conflict with the python io package)

This improves the speed of calling e.g., python simtools/applications/validate_schema_files.py --help by a factor of 4!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (7fa1f84) 99.30% compared to head (550c286) 99.30%.
Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #682   +/-   ##
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  Coverage   99.30%   99.30%           
=======================================
  Files          39       40    +1     
  Lines        3573     3575    +2     
=======================================
+ Hits         3548     3550    +2     
  Misses         25       25           

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[VictorBarbosaMartins]

Thanks for these updates, it is improving also in the direction of #665.
I left only one comment/suggestion.

[VictorBarbosaMartins]

It is good to have all the hdf5 functions together, but this function is not actually an io as it does not deal with input and output. Instead, if fills the table. Maybe we should call the module hdf5_handler instead?

[GernotMaier]

Thanks - this is a good suggestion. I've renamed io_hdf5 to hd5_handler.

Waiting for the tests and will merge when successful.