feat: add course import page

[rpenido]

Description

Describe what this pull request changes, and why. Include implications for people using this change.
Design decisions and their rationales should be documented in the repo (docstring / ADR), per
OEP-19, and can be linked here.

Useful information to include:

• Which user roles will this change impact? Common user roles are "Learner", "Course Author",
  "Developer", and "Operator".
• Include screenshots for changes to the UI (ideally, both "before" and "after" screenshots, if applicable).

Supporting information

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Be sure to check they are publicly readable, or if not, repeat the information here.

Testing instructions

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Other information

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• Does this change depend on other changes elsewhere?
• Any special concerns or limitations? For example: deprecations, migrations, security, or accessibility.

Best Practices Checklist

We're trying to move away from some deprecated patterns in this codebase. Please
check if your PR meets these recommendations before asking for a review:

• Any new files are using TypeScript (.ts, .tsx).
• Deprecated propTypes, defaultProps, and injectIntl patterns are not used in any new or modified code.
• Tests should use the helpers in src/testUtils.tsx (specifically initializeMocks)
• Do not add new fields to the Redux state/store. Use React Context to share state among multiple components.
• Use React Query to load data from REST APIs. See any apiHooks.ts in this repo for examples.
• All new i18n messages in messages.ts files have a description for translators to use.
• Imports avoid using ../. To import from parent folders, use @src, e.g. import { initializeMocks } from '@src/testUtils'; instead of from '../../../../testUtils'

[openedx-webhooks]

Thanks for the pull request, @rpenido!

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[codecov]

Codecov Report

❌ Patch coverage is 57.89474% with 16 lines in your changes missing coverage. Please review.
✅ Project coverage is 94.72%. Comparing base (f116740) to head (807108b).

Files with missing lines	Patch %	Lines
...brary-authoring/import-course/CourseImportPage.tsx	54.16%	9 Missing and 2 partials ⚠️
src/library-authoring/data/apiHooks.ts	25.00%	3 Missing ⚠️
src/library-authoring/data/api.ts	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2580      +/-   ##
==========================================
- Coverage   94.78%   94.72%   -0.06%     
==========================================
  Files        1225     1228       +3     
  Lines       27399    27436      +37     
  Branches     6151     6172      +21     
==========================================
+ Hits        25969    25990      +21     
- Misses       1359     1373      +14     
- Partials       71       73       +2     

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