Add lowmemory preference, keep stateless as an alias

[jmacd]

Update "stateless" names to "lowmemory" throughout the code, for clarity.

Description:

Link to tracking Issue:

Fixes #347.

Documentation: Updated.

[codecov-commenter]

Codecov Report

Attention: 1 lines in your changes are missing coverage. Please review.

Comparison is base (3b55ac7) 89.60% compared to head (4a33a52) 89.60%.

❗ Current head 4a33a52 differs from pull request most recent head 93b1904. Consider uploading reports for the commit 93b1904 to get more accurate results

Files	Patch %	Lines
pipelines/metrics.go	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #597   +/-   ##
=======================================
  Coverage   89.60%   89.60%           
=======================================
  Files          62       62           
  Lines        3686     3686           
=======================================
  Hits         3303     3303           
  Misses        285      285           
  Partials       98       98           

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