* Add login page illustration (#39299)

* Move Metabot setting to a new place

* Add setting for login page illustration

* fix UI styling

* Fix not able to upload the same file twice

* Update the admin > appearance > conceal metabase copy

* Prepare the component for tests

* Add some unit tests

* Prevent settings not saved sometimes

After setting the value to/from `custom` one of the setting could be
failed to save, I suspect this happens because the race condition from
trying to save the setting values relatively at the same time.

* Make unit tests easier to read

* Add all unit test test cases

* Add basic E2E test

* Show fallback icon for broken images

* Make use of the proper component

* Update the comment to affect the reality

* Add an error message when file size is over 2MB

* Show an error message when the file size > 2MB

* Add the error message tests

* Preserve the preview image aspect-ratio

* Detect corrupted images

* Fix failing unit tests

* Address feedback: Type

* Feedback: Create meaningful variables

* Feedback: Make selector API more sensible

* Prevent race condition

Makes sure we save the settings completely before making other actions
that also change settings otherwise, there could be race conditions.

* Feedback: tighten up a type

* Feedback: Fix inconsistency callback calls

* 2. Add the rest 3 illustration settings (#40487)

* Add the rest 3 illustration settings

* Don't make the X icon feel lonely

* Fix illustration widget saving

* Fix type error

* 3. Update the select UX to match new design (#40491)

* Update the select UX to match new design

* Move info dot next to file upload button

* Simplify IllustrationWidget API

* Update setting title copy

* Clean up test comments

* Feedback: Clarify `any` type

* Feedback: Use shorthand object creation

Co-authored-by: Denis Berezin <denis.berezin@metabase.com>

* Feedback: Use global CSS glass instead of inlining values

Co-authored-by: Denis Berezin <denis.berezin@metabase.com>

* Feedback: Remove unnecessary curly brackets in JSX

Co-authored-by: Denis Berezin <denis.berezin@metabase.com>

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Co-authored-by: Denis Berezin <denis.berezin@metabase.com>

* 4. Connect illustrations to new setting values (#40139)

* Wire landing page illustration to the setting value

* Wire the unsubscribe page to the setting value

* Prepare no rows error to be wired to the setting value

* Wire no question results illustration to the setting value

* Wire no search results illustration to setting value

* Fix error from fixing conflict

* Fix required unnecsseary prop on Image

* Use Image component

* Link dashboard card no results image to the setting value

* Move the no data results to more a generic directory

* Link collection picker no results image to the setting value

* Make illustrations more accessible

* Fix failed tests

* Test unscribe page illustration + test no illustration

* Add landing page tests

* Simplify Cypress selectors

* Refactor: Rename settings to match the new requirements

No question data -> No Data
No search results -> No object

These changes are made so, these 2 settings are generic enough to
include other illustrations later on.

* Add no data illustration test

* Add no object illustration tests

* Fix unsubscribe page background style

* Fix not able to build static viz

* 5. Follow-up on milestone 1 (#40710)

* Update custom background illustration scale behavior

* Remove the need to put an SVG file in static folder

* Fix test from rebasing off master with @testing-library/user-event upgrade

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Co-authored-by: Denis Berezin <denis.berezin@metabase.com>