fix: clean up invalid breadcrumb usages

[bradenmacdonald]

Description

When trying to pull in the newest version of Paragon, some type errors were showing up. I'm fixing some of them in openedx/paragon#4077 but others should be fixed in this repo.

The Paragon Breadcrumb label is used as a key in various places and so should be a string. It also needs to be unique, which seems dumb but that's how it's implemented. So I've changed the container changes preview "Back" breadcrumb from using a paragon icon to using a unicode left arrow:

Before	After

The difference is hardly noticeable, but this way it has the correct string type. If we really need the icon, we could just change this to a horizontal Stack instead of a Breadcrumb.

I also fixed some missing i18n for the word "Back", and changed a user-visible message to not include the term "Breadcrumb" which is a technical term that users may not know.

I also changed target to currentTarget in an event handler. For an element with no children, these will always be the same, but with the changes in openedx/paragon#4077 , only currentTarget will have the correct HTMLElement typing required to access data- attributes, because in theory the target value could be a totally different child element.

Supporting information

Together with openedx/paragon#4077 , this will unblock #2765 .

Testing instructions

Check that the "Library Updates" page is working as normal.

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'

Private ref: MNG-4846

[openedx-webhooks]

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 94.99%. Comparing base (4787490) to head (b25ed91).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2811   +/-   ##
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  Coverage   94.99%   94.99%           
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  Files        1256     1256           
  Lines       28800    28800           
  Branches     6337     6337           
=======================================
  Hits        27358    27358           
  Misses       1384     1384           
  Partials       58       58           

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[ChrisChV]

@bradenmacdonald The code looks good! But, in my instance, the change is noticeable:

[navinkarkera]

@bradenmacdonald Yes, it looks a bit weird. The unicode arrow looks small.

[bradenmacdonald]

@ChrisChV @navinkarkera Weird, I wonder why it's so different for you guys. I thought with web fonts these days, things would be more consistent than that. How about I just change it to not use Breadcrumb at all then? Just having a "back" button may not really be a proper usage of breadcrumb anyways (?) A horizontal stack will work just as well.