Encode build_options in base64

[pmachapman]

Partial fix for #966.

Requires: sillsdev/machine.py#330.

I will implement build_option constraints separately in another PR, as those will be implemented at the API boundary.

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This change is 

[codecov-commenter]

Codecov Report

❌ Patch coverage is 66.66667% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 71.81%. Comparing base (c885316) to head (d3d5348).

Files with missing lines	Patch %	Lines
...ment/Services/StatisticalClearMLBuildJobFactory.cs	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #992      +/-   ##
==========================================
- Coverage   71.82%   71.81%   -0.01%     
==========================================
  Files         374      374              
  Lines       20278    20290      +12     
  Branches     2686     2686              
==========================================
+ Hits        14564    14572       +8     
- Misses       4647     4651       +4     
  Partials     1067     1067              

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[ddaspit]

@ddaspit partially reviewed 5 files and all commit messages, and made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on Enkidu93).

[Enkidu93]

@Enkidu93 partially reviewed 5 files and all commit messages, and made 1 comment.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on pmachapman).