R4R: x/mock/simulation cleanup and re-org

[rigelrozanski]

NOTE this is rebased on 0.26 so should be merged after that

Due to the form of these changes, I suggest reviewing by just manually going through the commits (which I made many intentionally for this reason) as well as just snooping around x/mock/simulation/

This PR cleans up the simulation module but doesn't change it's functionality. Mostly:

• lots of whitespace improvements
• heavy indentation reduction
• introduction of helper structs, more functionality as properties of these objects
• heavy function reorg, elimination of grouped types file as per new conventions

---

• Linked to github-issue with discussion and accepted design OR link to spec that describes this work.
• Wrote tests
• Updated relevant documentation (docs/)
• Added entries in PENDING.md with issue #
• rereviewed Files changed in the github PR explorer

---

For Admin Use:

• Added appropriate labels to PR (ex. wip, ready-for-review, docs)
• Reviewers Assigned
• Squashed all commits, uses message "Merge pull request #XYZ: [title]" (coding standards)

[codecov]

Codecov Report

Merging #2720 into develop will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff            @@
##           develop    #2720   +/-   ##
========================================
  Coverage    56.89%   56.89%           
========================================
  Files          155      155           
  Lines         9751     9751           
========================================
  Hits          5548     5548           
  Misses        3825     3825           
  Partials       378      378

[cwgoes]

Thanks @rigelrozanski! I did indeed review commit-by-commit, which was pretty straightforward - LGTM.

Will need to be merged after #2718.

[cwgoes]

Also this is going to conflict with #2682 and #2683, so we should either merge those or this first.

[cwgoes]

I'm going to merge this since it has two reviews, doesn't change the state machine, and I need to work on these files.