refactor: Use formik and yup, and simplify hooks

[xitij2000]

Description

This change converts the Image Editor Modal to TypeScript and simplifies the hooks switching to Formik + Yup for form validation.

It updates the tests to check the behaviour of the component as a whole rather than testing small components.

This lays the groundwork for the CSS editor work.

Supporting information

• Allow Authors to Apply CSS Classes to Images platform-roadmap#494
• Reduce vertical spacing between field titles and inputs in the Studio image editor platform-roadmap#493
• Improve usability of the alt text control in the Studio image editor platform-roadmap#492

Testing instructions

• Compare the before and after shots of the image editor, the only changes should be those from the following two PRs:
  • Improve usability of the alt text control in the Studio image editor platform-roadmap#492
  • Reduce vertical spacing between field titles and inputs in the Studio image editor platform-roadmap#493

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).
• Avoid propTypes and defaultProps 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.
• Avoid using ../ in import paths. To import from parent folders, use @src, e.g. import { initializeMocks } from '@src/testUtils'; instead of from '../../../../testUtils'

[openedx-webhooks]

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[xitij2000]

Changed because title is only supposed to be a string and not a ReactNode.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 95.55%. Comparing base (0188698) to head (d852e1d).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2993      +/-   ##
==========================================
+ Coverage   95.52%   95.55%   +0.03%     
==========================================
  Files        1393     1392       -1     
  Lines       32969    32925      -44     
  Branches     7592     7581      -11     
==========================================
- Hits        31493    31461      -32     
+ Misses       1408     1398      -10     
+ Partials       68       66       -2     

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