Have all strategy response types be AttrDict (not bytes)

[CasperWA]

Description:

Closes #86

By "all", is meant that all strategy methods that previously returned bytes, now return an oteapi.models.AttrDict.
It is equivalent to a MutableMapping, but is also a pydantic BaseModel.

The demo notebook, as well as all the unit tests, have also been updated accordingly.

Type of change:

• Bug fix.
• New feature.
• Documentation update.

Checklist for the reviewer:

This checklist should be used as a help for the reviewer.

• Is the change limited to one issue?
• Does this PR close the issue?
• Is the code easy to read and understand?
• Do all new feature have an accompanying new test?
• Has the documentation been updated as necessary?

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Comparison is base (9c048cc) 90.67% compared to head (e591783) 90.74%.
Report is 1 commits behind head on master.

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Additional details and impacted files

@@            Coverage Diff             @@
##           master     #134      +/-   ##
==========================================
+ Coverage   90.67%   90.74%   +0.06%     
==========================================
  Files          26       26              
  Lines         429      432       +3     
==========================================
+ Hits          389      392       +3     
  Misses         40       40              

Flag	Coverage Δ
linux	90.74% <100.00%> (+0.06%)	⬆️
windows	90.04% <100.00%> (+0.07%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
otelib/backends/python/base.py	76.36% <100.00%> (ø)
otelib/backends/python/dataresource.py	81.81% <100.00%> (+0.56%)	⬆️
otelib/backends/services/base.py	97.95% <100.00%> (ø)
otelib/backends/strategies.py	95.74% <100.00%> (ø)
otelib/backends/utils.py	100.00% <100.00%> (ø)
otelib/pipe.py	100.00% <100.00%> (ø)

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[daniel-sintef]

Makes me very queezy. I really dislike backwards-incompatible changes [if I am not mistaken] the benefit to me is not very clear.

[daniel-sintef]

Unclear, need to think more. In general I am extremely biased against backwards-incompatible changes

[CasperWA]

Makes me very queezy. I really dislike backwards-incompatible changes [if I am not mistaken] the benefit to me is not very clear.

That's completely fair.
This is indeed backwards-incompatible in terms of what users can expect.

For the reasoning and any discussion about this I'd refer you to the issue this PR is trying to close: #86. Feel free to jump-start the discussion there with some thoughts.