Add a helper for setting RNG seed

[saitcakmak]

Summary: Adds a helper & a context manager that can be used to set the RNG seed for numpy, pytorch & the native random module.

Updates previous usage of botorch manual_seed (and some torch.manual_seed) with the new helper.

Differential Revision: D56738900

[codecov-commenter]

Codecov Report

Attention: Patch coverage is 98.80952% with 1 lines in your changes are missing coverage. Please review.

Project coverage is 95.31%. Comparing base (1be47e1) to head (5d70f66).

Files	Patch %	Lines
ax/utils/testing/core_stubs.py	50.00%	1 Missing :warning:

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #2408   +/-   ##
=======================================
  Coverage   95.30%   95.31%           
=======================================
  Files         495      497    +2     
  Lines       48427    48491   +64     
=======================================
+ Hits        46153    46217   +64     
  Misses       2274     2274           

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