Include sources for validation error formatted data

[pierlon]

Summary

Fixes #5825

Checklist

• My code is tested and passes existing tests.
• My code follows the Engineering Guidelines (updates are often made to the guidelines, check it out periodically).

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[codecov]

Codecov Report

Merging #5835 (f5efb19) into develop (e05b910) will increase coverage by 0.01%.
The diff coverage is 88.88%.

@@              Coverage Diff              @@
##             develop    #5835      +/-   ##
=============================================
+ Coverage      75.13%   75.14%   +0.01%     
- Complexity      5647     5655       +8     
=============================================
  Files            210      210              
  Lines          16961    16981      +20     
=============================================
+ Hits           12743    12760      +17     
- Misses          4218     4221       +3     

Flag	Coverage Δ	Complexity Δ
javascript	75.93% <ø> (ø)	0.00 <ø> (ø)
php	75.11% <88.88%> (+0.01%)	0.00 <11.00> (ø)

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Impacted Files	Coverage Δ	Complexity Δ
...validation/class-amp-validation-error-taxonomy.php	50.30% <88.00%> (+0.40%)	541.00 <11.00> (+8.00)
...s/validation/class-amp-validated-url-post-type.php	66.08% <100.00%> (+0.04%)	447.00 <0.00> (ø)

[westonruter]

I realize here that it's possible that the sources may not be specifically for this term. Specifically, it's possible for an error to occur multiple times on a URL, and each time the source may different. That does complicate things here, however, since the {{$taxonomy}}_row_actions filter doesn't pass any index. Perhaps that could be captured by by setting an index to 0 before rendering the table?

Then with each invocation of filter_tag_row_actions the index could be incremented. The index can then be provided from filter_tag_row_actions to get_error_details_json in addition to the $term (which would actually be redundant here), since the error could then be obtained in get_error_details_json here via $validation_errors[ $index ].

[pierlon]

@westonruter I think I have it resolved in 6af38a9.

[westonruter]

Rebasing to include #5837 along with a couple additional commits.