Add custom jsonfieldname linter to ensure Go field name matches JSON tag name

[gmlewis]

Note that there are many Go field names that do not match the JSON tag names, but changing them all would be a massive breaking API change that is probably unnecessary, and can instead be addressed on a one-by-one basis.

Additionally, one JSON tag had a typo which I've fixed in this PR.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 91.50%. Comparing base (b6248e6) to head (54a2ba5).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@ Coverage Diff @@## master #3757 +/- ##
=======================================
Coverage 91.50% 91.50% =======================================
Files 190 190 Lines 17007 17007 =======================================
Hits 15562 15562 Misses 1257 1257 Partials 188 188 

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[gmlewis]

@stevehipwell - @alexandear - @zyfy29 - might you have time for a code review? Thank you!

[gmlewis]

Thank you, @alexandear! I believe I've addressed your feedback.
Please take another look when you have a chance.