Reduce ZCC Runtimes

[NihalHarish]

Description of changes:

• This PR reduces the runtime of the ZCC unit tests
• We should ideally move save_all tests to nightly

Style and formatting:

I have run pre-commit install to ensure that auto-formatting happens with every commit.

Issue number, if available

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[codecov-commenter]

Codecov Report

Merging #315 into master will decrease coverage by 2.80%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #315      +/-   ##
==========================================
- Coverage   84.36%   81.56%   -2.81%     
==========================================
  Files          86       86              
  Lines        6352     6352              
==========================================
- Hits         5359     5181     -178     
- Misses        993     1171     +178     

Impacted Files	Coverage Δ
smdebug/pytorch/__init__.py	0.00% <0.00%> (-100.00%)	⬇️
smdebug/pytorch/singleton_utils.py	0.00% <0.00%> (-100.00%)	⬇️
smdebug/pytorch/collection.py	0.00% <0.00%> (-90.00%)	⬇️
smdebug/pytorch/hook.py	0.00% <0.00%> (-80.33%)	⬇️
smdebug/pytorch/utils.py	0.00% <0.00%> (-43.59%)	⬇️
smdebug/rules/action/stop_training_action.py	61.53% <0.00%> (-15.39%)	⬇️
smdebug/rules/req_tensors.py	79.16% <0.00%> (-11.12%)	⬇️
smdebug/core/tfevent/util.py	83.87% <0.00%> (-6.46%)	⬇️
smdebug/tensorflow/callable_cache.py	78.26% <0.00%> (-4.35%)	⬇️
smdebug/rules/action/action.py	91.83% <0.00%> (-4.09%)	⬇️
... and 3 more

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[vandanavk]

save step 0,1,2,3. same on L222

[NihalHarish]

Leaving this PR open.
The performance concern was addressed in

#316

[vandanavk]

whats the next step on this pr?