docs: add TestSetRealm reference docs

[leohhhn]

Description

This PR adds TestSetRealm docs, as well as related docs. It also fixes up a few minor details.

Closes: #2273

Contributors' checklist...

• Added new tests, or not needed, or not feasible
• Provided an example (e.g. screenshot) to aid review or the PR is self-explanatory
• Updated the official documentation or not needed
• No breaking changes were made, or a BREAKING CHANGE: xxx message was included in the description
• Added references to related issues and PRs
• Provided any useful hints for running manual tests
• Added new benchmarks to generated graphs, if any. More info here.

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 54.63%. Comparing base (c5b999f) to head (484e898).
Report is 2 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2369   +/-   ##
=======================================
  Coverage   54.63%   54.63%           
=======================================
  Files         581      581           
  Lines       77967    77967           
=======================================
  Hits        42596    42596           
  Misses      32189    32189           
  Partials     3182     3182           

Flag	Coverage Δ
gnovm	60.06% <ø> (ø)

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