update textarea height and refocus when attaching files

What does this MR do?

Keep focus in textarea when attaching files Don't add 3 newlines after pasting a file in textarea

Are there points in the code the reviewer needs to double check?

• not 100% where test for this should go. I don't want to keep adding regression tests to, but directly testing the side effects of the click handler doesn't seem so great either. Suggestions?

Screenshots (if relevant)

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• [ ] Documentation created/updated
• [ ] API support added
• Tests
  • Added for this feature/bug
  • All builds are passing
• Conform by the merge request performance guides
• Conform by the style guides
• Branch has no merge conflicts with master (if it does - rebase it please)
• Squashed related commits together

What are the relevant issue numbers?

Closes #30008 (closed)

assigned to @psimyn

added 348 commits

• 7092d5cb...4dd841c9 - 347 commits from branch master
• 397eb0ad - update textarea height and refocus when attaching files

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added 946 commits

• 397eb0ad...7629c9ec - 945 commits from branch master
• 1d43ebf5 - update textarea height and refocus when attaching files

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added 116 commits

• 1d43ebf5...2b934a7f - 115 commits from branch master
• b0dc02e3 - update textarea height and refocus when attaching files

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added 1 commit

• ee65f5ee - update textarea height and refocus when attaching files

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marked the checklist item Changelog entry added, if necessary as completed

assigned to @filipa

approved this merge request

thank you so much for this. This bug is so annoying

@psimyn can you check what's wrong with this job https://gitlab.com/gitlab-org/gitlab-ce/builds/14517811?

I am going to set to MWPS :)

enabled an automatic merge when the pipeline for ee65f5ee succeeds

thanks @filipa! Made ee MR https://gitlab.com/gitlab-org/gitlab-ee/merge_requests/1669

merged

mentioned in commit ba1e9495

marked the checklist item All builds are passing as completed

Picked into 9-1-stable, will go into 9.1.0-rc5

mentioned in commit 83375c5e