Improve stringify test coverage

[gmlewis]

This PR adds missing structs and slices to the stringify tests for better test coverage.

[codecov]

Codecov Report

Merging #2320 (c235e4a) into master (6cd5d41) will increase coverage by 0.05%.
The diff coverage is n/a.

❗ Current head c235e4a differs from pull request most recent head 1bb88f3. Consider uploading reports for the commit 1bb88f3 to get more accurate results

@@ Coverage Diff @@## master #2320 +/- ##
==========================================
+ Coverage 97.87% 97.92% +0.05% 
==========================================
Files 117 115 -2 Lines 10402 10416 +14 ==========================================
+ Hits 10181 10200 +19 + Misses 154 148 -6 - Partials 67 68 +1 

Impacted Files	Coverage Δ
github/repos_contents.go	88.95% <0.00%> (-0.38%)	⬇️
github/github.go	97.64% <0.00%> (-0.10%)	⬇️
github/actions_artifacts.go	100.00% <0.00%> (ø)
github/actions_workflow_jobs.go	100.00% <0.00%> (ø)
github/actions_workflow_runs.go	100.00% <0.00%> (ø)
github/repos_actions_permissions.go
github/repos_actions_allowed.go
github/repos.go	98.70% <0.00%> (+0.04%)	⬆️
github/repos_stats.go	95.34% <0.00%> (+2.32%)	⬆️
github/misc.go	100.00% <0.00%> (+3.63%)	⬆️
... and 1 more

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[gmlewis]

@Parker77 - do you have time for a code review?

[Parker77]

LGTM!

[gmlewis]

Thank you, @Parker77 !
Merging.