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).