Add and pass regression tests for PerseusItem parser

[benchristel]

Issue: LEMS-2582

Test plan:

yarn test

[khan-actions-bot]

Gerald

Required Reviewers

• @Khan/perseus for changes to packages/perseus/src/perseus-types.ts, packages/perseus/src/widgets/graded-group/graded-group.tsx, packages/perseus/src/widgets/matrix/matrix.tsx, packages/perseus/src/util/parse-perseus-json/general-purpose-parsers/defaulted.ts, packages/perseus/src/util/parse-perseus-json/general-purpose-parsers/index.ts, packages/perseus/src/util/parse-perseus-json/general-purpose-parsers/pair.test.ts, packages/perseus/src/util/parse-perseus-json/general-purpose-parsers/pipe-parsers.test.ts, packages/perseus/src/util/parse-perseus-json/general-purpose-parsers/pipe-parsers.ts, packages/perseus/src/util/parse-perseus-json/general-purpose-parsers/pipe-parsers.typetest.ts, packages/perseus/src/util/parse-perseus-json/general-purpose-parsers/trio.test.ts, packages/perseus/src/util/parse-perseus-json/general-purpose-parsers/unknown.ts, packages/perseus/src/util/parse-perseus-json/perseus-parsers/categorizer-widget.ts, packages/perseus/src/util/parse-perseus-json/perseus-parsers/dropdown-widget.ts, packages/perseus/src/util/parse-perseus-json/perseus-parsers/expression-widget.ts, packages/perseus/src/util/parse-perseus-json/perseus-parsers/graded-group-widget.ts, packages/perseus/src/util/parse-perseus-json/perseus-parsers/hint.ts, packages/perseus/src/util/parse-perseus-json/perseus-parsers/iframe-widget.ts, packages/perseus/src/util/parse-perseus-json/perseus-parsers/images-map.ts, packages/perseus/src/util/parse-perseus-json/perseus-parsers/matrix-widget.ts, packages/perseus/src/util/parse-perseus-json/perseus-parsers/perseus-item.test.ts, packages/perseus/src/util/parse-perseus-json/perseus-parsers/perseus-item.ts, packages/perseus/src/util/parse-perseus-json/perseus-parsers/perseus-renderer.ts, packages/perseus/src/util/parse-perseus-json/perseus-parsers/radio-widget.ts, packages/perseus/src/util/parse-perseus-json/perseus-parsers/widget.ts, packages/perseus/src/util/parse-perseus-json/regression-tests/__snapshots__/parse-perseus-json-snapshot.test.ts.snap, packages/perseus/src/util/parse-perseus-json/regression-tests/data/categorizer-missing-static.json, packages/perseus/src/util/parse-perseus-json/regression-tests/data/dropdown-missing-version.json, packages/perseus/src/util/parse-perseus-json/regression-tests/data/hint-missing-images.json, packages/perseus/src/util/parse-perseus-json/regression-tests/data/iframe-missing-static.json, packages/perseus/src/util/parse-perseus-json/regression-tests/data/item-missing-answerArea.json, packages/perseus/src/util/parse-perseus-json/regression-tests/data/matrix-missing-version.json, packages/perseus/src/util/parse-perseus-json/regression-tests/data/orderer-option-missing-images.json, packages/perseus/src/util/parse-perseus-json/regression-tests/data/orderer-option-missing-widgets.json, packages/perseus/src/util/parse-perseus-json/regression-tests/data/question-missing-content.json, packages/perseus/src/util/parse-perseus-json/regression-tests/data/radio-choice-missing-content.json

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[github-actions]

Size Change: +527 B (+0.04%)

Total Size: 1.29 MB

Filename	Size	Change
packages/perseus/dist/es/index.js	422 kB	+527 B (+0.13%)

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	697 kB
packages/perseus-linter/dist/es/index.js	22.2 kB
packages/perseus/dist/es/strings.js	3.57 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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