feat(Sandbox): Run experiment in subprocess.

[moi90]

For example, this would allow trials to be inserted into a batch queue.

closes #xxxx

• Tests added
• Tests pass
• Coverage
• Documentation
• CHANGELOG entry

[codecov]

Codecov Report

❌ Patch coverage is 64.44444% with 32 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.43%. Comparing base (6824a67) to head (546c5fb).
⚠️ Report is 115 commits behind head on master.

Files with missing lines	Patch %	Lines
experitur/sandbox.py	64.44%	32 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #24      +/-   ##
==========================================
- Coverage   93.49%   91.43%   -2.06%     
==========================================
  Files          19       20       +1     
  Lines        1261     1355      +94     
==========================================
+ Hits         1179     1239      +60     
- Misses         82      116      +34     

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