Store groups as members of generator group

[wvandeun]

Stores CoreStandardGroups that are created or updated by a generator as members of the CoreGeneratorGroup.
Previously they were stored as children of the CoreGeneratorGroup, which created a weird behavior, especially in the UI where groups are shown hierarchically.

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 6 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
infrahub_sdk/query_groups.py	0.00%	6 Missing ⚠️

@@             Coverage Diff             @@
##           develop     #303      +/-   ##
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+ Coverage    70.38%   70.58%   +0.20%     
===========================================
  Files           81       81              
  Lines         7522     7499      -23     
  Branches      1467     1457      -10     
===========================================
- Hits          5294     5293       -1     
+ Misses        1844     1822      -22     
  Partials       384      384              

Flag	Coverage Δ
integration-tests	22.60% <0.00%> (+0.05%)	⬆️
python-3.10	45.56% <0.00%> (+0.12%)	⬆️
python-3.11	45.56% <0.00%> (+0.12%)	⬆️
python-3.12	45.56% <0.00%> (?)
python-3.9	44.40% <0.00%> (+0.12%)	⬆️
python-filler-3.12	24.05% <0.00%> (+0.06%)	⬆️

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Files with missing lines	Coverage Δ
infrahub_sdk/query_groups.py	46.87% <0.00%> (+6.47%)	⬆️

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