feat(inVideoQuiz): allow multiple in-video quiz problems at the same timestamp

[abhalsod-sonata]

• Removed duplicate timestamp validation from InVideoQuizEditor, allowing multiple problems to share the same timestamp.
• Updated quiz item handling in the Redux thunk actions to support expanded timemap formats, including legacy and multi-problem structures.
• Introduced new utility functions for normalizing problem IDs and jump-back fields, improving code organization and readability.
• Added comprehensive unit tests for new and existing functionality to ensure robustness and correctness.

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Support ticket:

• https://2u-internal.atlassian.net/browse/LP-242

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Summary

Updates the In-Video Quiz editor MFE to configure multiple problems at the same timestamp, with per-problem jump-back values. Removes duplicate-time validation and adds timemap/jump-back helpers with legacy data support on load and save.

Changes

Editor (InVideoQuizEditor/index.jsx)

• Remove duplicate-timestamp validation so multiple problems can share the same time (e.g. both at 01:30)
• Save/load round-trip via updated thunk helpers

Data layer (inVideoQuiz.js)

• normalizeProblemIds() — handle string or array timemap values
• expandTimemapToQuizItems() — load legacy + multi-problem timemaps into editor rows
• buildTimemapFromQuizItems() — save single string or array per timestamp
• buildJumpBackFromQuizItems() — save jump-back keyed by problem ID
• normalizeJumpBackField() / resolveQuizItemJumpBack() — legacy global MM:SS, time-keyed, and per-problem maps
• parseJumpBackField() — parse legacy plain jump-back strings from studio_view HTML

Tests

• New inVideoQuiz.test.js — 19 tests for timemap/jump-back helpers
• InVideoQuizEditor/index.test.jsx — save allowed with duplicate timestamps

Supported data formats

Format	Load	Save
Single problem per time	{"1:30": "id1"}	Same
Multiple problems per time	{"1:30": ["id1", "id2"]}	Same
Legacy time-keyed jump-back	{"1:30": "1:29"}	Per-problem on re-save
Per-problem jump-back	{"id1": "1:29", "id2": "1:45"}	Same

Test plan

• npm test -- inVideoQuiz passes
• npm test -- InVideoQuizEditor passes
• Studio: add 2 problems at 01:30 with different jump-backs → Save succeeds
• Reopen editor → both problems and jump-back values persist
• Legacy course (single problem, time-keyed jump-back) loads correctly in editor
• End-to-end with LMS: sequential quiz + jump-back after last problem