Refactor/deprecate some allocs

[jlnav]

Deprecation Module experiments

Experiments with deprecating old allocs, a new gen class for pregenerated work, and a deprecation module

[codecov]

Codecov Report

❌ Patch coverage is 53.84615% with 24 lines in your changes missing coverage. Please review.
✅ Project coverage is 76.54%. Comparing base (85c7a8c) to head (24e39b8).
⚠️ Report is 5 commits behind head on develop.

Files with missing lines	Patch %	Lines
libensemble/gen_classes/preloaded.py	44.44%	20 Missing ⚠️
libensemble/alloc_funcs/start_fd_persistent.py	0.00%	2 Missing ⚠️
...ble/alloc_funcs/start_persistent_local_opt_gens.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop    #1746      +/-   ##
===========================================
- Coverage    76.70%   76.54%   -0.16%     
===========================================
  Files           79       81       +2     
  Lines         8340     8392      +52     
  Branches      1289     1292       +3     
===========================================
+ Hits          6397     6424      +27     
- Misses        1681     1705      +24     
- Partials       262      263       +1     

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