SSS: Introduce ValidationResult type so things are standardized

[jeremywiebe]

Summary:

This is a tiny PR to introduce a validation result which is a subset of the PerseusScore, but since we use it all over the validation code, it seemed useful to create a type for it.

Issue: LEMS-2561

Test plan:

yarn typecheck
yarn test

[github-actions]

npm Snapshot: Published

Good news!! We've packaged up the latest commit from this PR (2d93d61) and published it to npm. You
can install it using the tag PR1993.

Example:

yarn add @khanacademy/perseus@PR1993

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

./dev/tools/bump_perseus_version.sh -t PR1993

[github-actions]

Size Change: 0 B

Total Size: 1.27 MB

ℹ️ View Unchanged

Filename	Size
packages/kas/dist/es/index.js	39 kB
packages/keypad-context/dist/es/index.js	760 B
packages/kmath/dist/es/index.js	4.27 kB
packages/math-input/dist/es/index.js	77.9 kB
packages/math-input/dist/es/strings.js	1.79 kB
packages/perseus-core/dist/es/index.js	1.48 kB
packages/perseus-editor/dist/es/index.js	688 kB
packages/perseus-linter/dist/es/index.js	22.2 kB
packages/perseus/dist/es/index.js	415 kB
packages/perseus/dist/es/strings.js	3.7 kB
packages/pure-markdown/dist/es/index.js	3.66 kB
packages/simple-markdown/dist/es/index.js	12.5 kB

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[handeyeco]

Makes sense, lgtm