Add an ability to cancel attaching file and redesign attaching files UI
What does this MR do?
- It adds an ability to cancel file uploading in textareas.
- It improves UX of textareas where attaching files are allowed.
Are there points in the code the reviewer needs to double check?
Please double check that JS code is in the right place.
Why was this MR needed?
It improves UX
Screenshots (if relevant)
| Stage | Desktop | Mobile |
|---|---|---|
| Before attaching |  |
 |
| Uploading |  |
 |
| Uploading complete |  |
 |
| Uploading error |  |
 |
Does this MR meet the acceptance criteria?
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Changelog entry added - Tests
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Added for this feature/bug -
All builds are passing
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Branch has no merge conflicts with master(if it does - rebase it please) -
Squashed related commits together
What are the relevant issue numbers?
Closes #15611 (closed), #24270 (closed), #28905 (closed), #32212 (closed).