Split StatefulMafsGraph and MafsGraph into separate files

[benchristel]

Each of these components used different helper functions and types defined
alongside them. I've moved each component into a separate file along with its
associated functions and types. This makes the files more cohesive, so it's
easier to see which groups of entities go together.

Issue: none

Test plan:

yarn test

[khan-actions-bot]

Gerald

Required Reviewers

• @Khan/perseus for changes to .changeset/smooth-rice-speak.md, packages/perseus/src/widgets/interactive-graphs/index.ts, packages/perseus/src/widgets/interactive-graphs/mafs-graph.test.tsx, packages/perseus/src/widgets/interactive-graphs/mafs-graph.tsx, packages/perseus/src/widgets/interactive-graphs/stateful-mafs-graph.test.tsx, packages/perseus/src/widgets/interactive-graphs/stateful-mafs-graph.tsx

---

Don't want to be involved in this pull request? Comment #removeme and we won't notify you of further changes.

[github-actions]

npm Snapshot: Published

Good news!! We've packaged up the latest commit from this PR (27ef937) and published it to npm. You
can install it using the tag PR1397.

Example:

yarn add @khanacademy/perseus@PR1397

If you are working in Khan Academy's webapp, you can run:

./dev/tools/bump_perseus_version.sh -t PR1397

[github-actions]

Size Change: -133 B (-0.02%)

Total Size: 854 kB

Filename	Size	Change
packages/perseus/dist/es/index.js	414 kB	-133 B (-0.03%)

ℹ️ View Unchanged

Filename	Size
packages/kas/dist/es/index.js	38.2 kB
packages/kmath/dist/es/index.js	4.26 kB
packages/math-input/dist/es/index.js	80.8 kB
packages/math-input/dist/es/strings.js	1.73 kB
packages/perseus-core/dist/es/index.js	906 B
packages/perseus-editor/dist/es/index.js	272 kB
packages/perseus-error/dist/es/index.js	866 B
packages/perseus-linter/dist/es/index.js	21.8 kB
packages/perseus/dist/es/strings.js	3.21 kB
packages/pure-markdown/dist/es/index.js	3.67 kB
packages/simple-markdown/dist/es/index.js	12.4 kB

_{compressed-size-action}

[codecov]

Codecov Report

Attention: Patch coverage is 98.11321% with 3 lines in your changes missing coverage. Please review.

Project coverage is 70.87%. Comparing base (f5711a3) to head (27ef937).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1397      +/-   ##
==========================================
+ Coverage   69.83%   70.87%   +1.04%     
==========================================
  Files         503      508       +5     
  Lines      105124   105212      +88     
  Branches     5339    11340    +6001     
==========================================
+ Hits        73414    74571    +1157     
+ Misses      31594    30641     -953     
+ Partials      116        0     -116     

Files	Coverage Δ
...es/perseus/src/widgets/interactive-graphs/index.ts	100.00% <100.00%> (ø)
...seus/src/widgets/interactive-graphs/mafs-graph.tsx	99.41% <97.05%> (-0.25%)	⬇️
...widgets/interactive-graphs/stateful-mafs-graph.tsx	98.38% <98.38%> (ø)

... and 121 files with indirect coverage changes

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[handeyeco]

My understanding is this is just splitting up one file into two. If that's the case and there are no changes to logic, I think this makes a lot of sense.