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 72.74%. Comparing base (d6a912c) to head (02cb18c).
⚠️ Report is 1 commits behind head on main.

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

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #992   +/-   ##
=======================================
  Coverage   72.74%   72.74%           
=======================================
  Files         392      392           
  Lines       21711    21723   +12     
  Branches     2820     2820           
=======================================
+ Hits        15794    15803    +9     
- Misses       4794     4797    +3     
  Partials     1123     1123           

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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).