Add vocs sampling gens

[shuds13]

• Adds remaining sampling generators as gest-api gens.
• Updates initial_sample_method to accept sample constructed with options
• Keeps string option for initial_sample_method for simple samplers.
• Adds test for LHS class and using initial_sample_method with sampler instance.

Remaining methods to be tested when tests are bulk updated to use VOCS.

[codecov]

Codecov Report

❌ Patch coverage is 34.58647% with 87 lines in your changes missing coverage. Please review.
✅ Project coverage is 91.78%. Comparing base (05fa70f) to head (6824bb3).
⚠️ Report is 12 commits behind head on develop.

Files with missing lines	Patch %	Lines
libensemble/gen_classes/sampling.py	36.58%	78 Missing ⚠️
libensemble/utils/runners.py	0.00%	9 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##           develop    #1728       +/-   ##
============================================
+ Coverage    77.81%   91.78%   +13.97%     
============================================
  Files           79       79               
  Lines         8191     8317      +126     
  Branches      1264     1279       +15     
============================================
+ Hits          6374     7634     +1260     
+ Misses        1578      481     -1097     
+ Partials       239      202       -37     

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[jlnav]

I'm assuming when tests are bulk-updated is when the old versions will be deprecated/deleted?