Rename metadata_container to objects

[AleksanderWWW]

Before submitting checklist

• Did you update the CHANGELOG? (not for test updates, internal changes/refactors or CI/CD setup)
• Did you ask the docs owner to review all the user-facing changes?

[codecov]

Codecov Report

Attention: Patch coverage is 81.81818% with 16 lines in your changes are missing coverage. Please review.

Project coverage is 74.09%. Comparing base (0fc56bc) to head (440baf9).

Files	Patch %	Lines
src/neptune/attributes/atoms/string.py	50.00%	1 Missing ⚠️
src/neptune/attributes/attribute.py	50.00%	1 Missing ⚠️
src/neptune/attributes/namespace.py	66.66%	1 Missing ⚠️
src/neptune/attributes/series/string_series.py	50.00%	1 Missing ⚠️
src/neptune/attributes/utils.py	0.00%	1 Missing ⚠️
src/neptune/handler.py	75.00%	1 Missing ⚠️
src/neptune/internal/backgroud_job_list.py	50.00%	1 Missing ⚠️
src/neptune/internal/background_job.py	50.00%	1 Missing ⚠️
...internal/hardware/hardware_metric_reporting_job.py	50.00%	1 Missing ⚠️
...tune/internal/signals_processing/background_job.py	75.00%	1 Missing ⚠️
... and 6 more

Additional details and impacted files

@@             Coverage Diff             @@
##           dev/2.0    #1696      +/-   ##
===========================================
- Coverage    74.12%   74.09%   -0.03%     
===========================================
  Files          338      338              
  Lines        16496    16495       -1     
===========================================
- Hits         12227    12222       -5     
- Misses        4269     4273       +4     

Flag	Coverage Δ
macos	76.99% <81.81%> (+<0.01%)	⬆️
py3.7	77.22% <81.81%> (+<0.01%)	⬆️
ubuntu	77.08% <81.81%> (+<0.01%)	⬆️
unit	77.22% <81.81%> (+<0.01%)	⬆️
windows	75.74% <81.81%> (+<0.01%)	⬆️

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