Reworked series values models and protocol buffers added

[Raalsky]

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 85.13514% with 11 lines in your changes are missing coverage. Please review.

Project coverage is 73.11%. Comparing base (f5e087c) to head (59d4069).

Files	Patch %	Lines
...pi/proto/neptune_pb/api/model/series_values_pb2.py	64.70%	6 Missing ⚠️
...eptune/internal/backends/hosted_neptune_backend.py	0.00%	3 Missing ⚠️
src/neptune/api/models.py	97.82%	1 Missing ⚠️
src/neptune/attributes/series/fetchable_series.py	83.33%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1738      +/-   ##
==========================================
- Coverage   76.81%   73.11%   -3.71%     
==========================================
  Files         243      244       +1     
  Lines       12955    12812     -143     
==========================================
- Hits         9952     9368     -584     
- Misses       3003     3444     +441     

Flag	Coverage Δ
e2e	?
e2e-management	?
e2e-s3	?
e2e-s3-gcs	?
e2e-standard	?
py3.10	?
py3.11	?
py3.12	?
py3.7	73.11% <85.13%> (-3.08%)	⬇️
py3.8	?
py3.9	?
ubuntu	73.07% <85.13%> (-3.69%)	⬇️
unit	73.11% <85.13%> (-0.64%)	⬇️
windows	72.01% <85.13%> (-4.44%)	⬇️

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[Raalsky]

E2E: https://github.com/neptune-ai/neptune-client/actions/runs/8662412491

[szysad]

LGTM!